Question

How do I find y on 13?

Answer 1

9y - 77 = 12x - 28

therefore you first need to find x:
7x + 12 = 12x - 28
-5x = -40
x = 8

then you use x = 8
9y - 77 = 12×8 - 28
9y = 96 - 28 + 77
9y = 145
y = 16.11