Question 442979
Notice that with -6x +y =57, y has a coefficient of 1. This will be a good choice for substitution.

Solve for y. 

y = 57+6x

Plug 57+6x back in the other equation where you see y.

4x + 5(57+6x) = 13
4x + 285 + 30x = 13
34x = -272
x=-8

Plug -8 back into either equation.

-6(-8) + y = 57
48 + y = 57
y = 9

So our solution is (-8,9) {{{x=-8}}}{{{y=9}}}.

Let's check to make sure this works.

4(-8) + 5(9) = -32 + 45 = 13
-6(-8) + 9 = 48 + 9 = 57 

So it works.

Hope this helped!