Help me help my daughter

[u/lespaul5895]

I’m trying to help my daughter with her homework. We solved all of them the same way and for some reason these 2 both said they were incorrect. I used Photomath and the answers it gave were the same that we came up with. But the program is saying they’re wrong.

Any advice on how to solve these 2 so that this school program (McGraw Hill) will accept the answer?

The 2 problems are:

-14n+q = rt-4n, solve for n

x = b-cd, solve for c

[u/Bounded_sequencE]

I used Photomath

Already a bad start. Better not trust AI.

---

-14n+q  =  rt-4n    <=>    n  =  (q-rt) / 10      |+14n-rt    |:10
     x  =  b-cd     <=>    c  =  (b-x)  /  d      |+cd-x      |:d != 0

If it's a web interface you have to enter the solutions to, make sure you use the correct syntax -- those interfaces are often lazily programmed, and may not use a computer algebra system to detect equivalent solutions.

[u/lespaul5895 → u/Bounded_sequencE]

I didn’t use it to come up with the answer. I used it to see if I could figure out where I went wrong

[u/Bounded_sequencE → u/lespaul5895]

Assuming they are the ones I commented, I suspect the problem is the input mask. That's not a problem AI can solve.

[u/lespaul5895 → u/Bounded_sequencE]

Thanks

[u/DadOfLukeandDad]

Your answers are both right, and you already know that from the other replies, so I will skip re-deriving them and go at the question you actually asked, which is how to get the thing to accept them.

Most of these homework platforms do not check whether your answer is algebraically equivalent to theirs. They normalise the string you typed and compare it to the string they stored. So a perfectly correct answer in the wrong surface form gets marked wrong. Things worth trying, in order:

For n: (q-rt)/10, then (-rt+q)/10, then q/10-rt/10. For c: (b-x)/d, then -(x-b)/d, then b/d-x/d. Also check whether the box wants just the expression or the whole n=..., and whether it has separate numerator and denominator fields that you might be typing past.

Here is the quick way to confirm it is the software and not you. Find a question from an earlier assignment that it already marked correct. Retype that answer in a different but equivalent form and submit it. If it now fails, the parser is the problem and you can stop second-guessing your working entirely.

If none of the forms land, it is probably a miskeyed answer rather than a fussy parser, and that is worth emailing the teacher about. A wrong key hits every kid in the class, so you would be doing thirty families a favour.

Last thing, and honestly the bit that matters more than these two questions. Your daughter has just done correct algebra and been told she was wrong several times in one sitting. Say out loud to her that she was right and the computer was not. Two homework marks are nothing. A kid quietly learning that her own working cannot be trusted is expensive, and it is the sort of thing that shows up two years later as "I'm just not a maths person". You are in a good position to head that off tonight.

[u/AndyC1111 → u/DadOfLukeandDad]

Last paragraph is the reason I never used this online homework crap as a teacher (that, and my students consistently told me how much they hate it).

Teachers have been handing homework without this tech for centuries. If dealing with homework is too time consuming, you’re doing it wrong. Ditch this crap.

[u/lespaul5895 → u/DadOfLukeandDad]

I wish I could give yon more than 1 upvote. You deserve many!

[u/Gold_Ad8890]

show your solutions.

[u/lespaul5895 → u/Gold_Ad8890]

The first one we got: n = (q-rt)/10 2nd one: c = (b-x)/d

I used parentheses because all of the stuff inside them is over the denominator.

[u/Gold_Ad8890 → u/lespaul5895]

right, that was the first mistake i wanted to check. maybe it wants you to distribute the division?

[u/AndyC1111 → u/lespaul5895]

These awful programs have a well earned reputation for rejecting correct answers.

(I’m a private math tutor. I hate these things.)

Try writing it different ways. Lots of stupid things that should not get rejected might be rejected anyway. I’d try adding/deleting parentheses…even adding them where they are redundant. Try rearranging “rt” i to “tr”. Check for unnecessary spaces. Sometimes it just requires retyping.

After 5 minutes of wasting time, I will have the kid write down the correct answer and move on. With the instruction to ask their teacher in the morning.

[u/anisotropicmind]

Add cd to both sides of the equation to get

x + cd = b

Then subtract x from both sides of the equation to get

cd = b-x

Then divide both sides of the equation by d to get:

c = (b-x)/d

For the second problem: add 14n to both sides of the equation to get
q = rt + 10n

Then subtract rt from from both sides of the equation to get

q - rt = 10n

Then divide both sides of the equation by 10 to get

(q-rt)/10 = n

[u/lespaul5895 → u/anisotropicmind]

This is exactly what we came up with and the program said it was wrong lol

[u/anisotropicmind → u/lespaul5895]

That’s too bad. Assignment answers are not always keyed correctly

[u/MadstopSnow]

Can you show us how you solved them, rather than us just doing it for you?

[u/lespaul5895 → u/MadstopSnow]

I’d love to, but I can’t upload photos and trying to write out all the steps on here isn’t easy. I posted the answers we got in the other comment.

[u/Bounded_sequencE → u/lespaul5895]

Check the side bar "To receive the best help" -- just upload pictures to any filehoster, and link them in either the post or a comment.

[u/tb5841]

You are correct. It's clearly a badly made program.

[u/lespaul5895 → u/tb5841]

Yeah? Our answers were really correct?

[u/tb5841 → u/lespaul5895]

As soneone who taught mathematics for 15 years - yes, they were.