Question

x = -7y + 34 and x + 7y = 32

Answer 1

just plug in x for -7y + 34 and simplify the equation.

Answer 2

-7y + 34 +x +7y = 32

so the -7y and +7y cancel and you are left with 34+x = 32
32-34 = -2
so x = -2