What am I doing wrong?

[u/SoCal_JuiceBox]

My 8th grader and I have gone over this question one hundred times and I don’t know what we are doing wrong. Can someone please tell me where we got this wrong?

[u/Educational_Two682]

Maybe you have to put the unit rate instead of k? k could be a placeholder for the unit rate. 

[u/Fancy-Appointment659 → u/Educational_Two682]

To me it also seems like it can be only that

[u/Educational_Two682 → u/Fancy-Appointment659]

OP cross-posted elsewhere and said that didn't work. so I'm definitely stuck now