What is did to solve this problem was i wrote this down to get this figured out.
7x + 3y - 2 + 6x - 1 + y^2
The first thing I did to this problem was i took 6x and change it to a -6x because I'm subtracting it from 7x which 7x - 6x is just x cause there is an understood 1 next to it. So i rewrote the problem as x + 3y - 2 - 1 + y^2
So then i took the -2 and subtract it to 1 which is -3
So the answer I have is x+3y-3+y^2
Hope this helped! :)
~ShadowKitty101