Ah hah ! This is exactly what I was telling you about in the other answer.
A pair of angles that are formed by 2 lines and DON't share a side are called
"vertical angles", and a pair of vertical angles are always equal.
In this problem, the two angles on the sides facing each other are vertical angles, and that tells you that they're equal.
So you can immediately write 4y - 8 = 79 + y ,
and then you can easily solve that and find the value of 'y' .