wat is the answer to the following equation by using the substitution method?

x=6y-4
x=-2+28

I think you have a typo and I will assume your second equation is

x = -2y + 28

sub the first equation into the second ....

2nd .... x = -2y + 28
6y-4 = -2y + 28
8y = 32
y = 4

back in first
x = x = 6(4)-4 = 20

x=20
y=4