Solve the following system of equations using the substitution method:5x-7y=-18 and 4x+3y=20

Answer 1

from the 2nd:
4x = 20 - 3y
x = 5 - (3/4)y

plug into the 1st:
5x - 7y = -18
5(5 - (3/4)y) - 7y = -18
25 - 15y/4 - 7y = -18
-43y/4 = -43
y = -43(-4/43) = 4
x = 5 - (3/4)4 = 2

(substitution would have been my last choice in the methods to solve this, I would have used elimination)