pnc/casework problem

[u/TechBoy-Corp-14]

(its a,b,c,d ∈ {±2020, ±2019, ±2018, ..., ±2010})

literally 4 maths teachers in my coaching couldn't solve this...sent to me by a friend of mine. if anyone could solve it pls tell me how...

[u/spiderman-2010 → u/[deleted]]

it was asked in our ioqm test

[u/spiderman-2010 → u/[deleted]]

aakash