y = 4x - 9

Question

-7x - 6y = -39

Answer 1

Perfectly set up for substitution
sub y = 4x - 9 into the 2nd equation:
-7x - 6(4x-9) = -39
-7x - 24x + 54 = -39
-31x = -93
x = 3

then y = 4(3) - 9 = 3