To solve this system of equations, we will first substitute equations 1 and 2 into equation 3.

From equation 1: у = -3x + 4
Substitute this into equation 3: x + 8 - 6(-3x + 4) = 0
x + 8 + 18x - 24 = 0
19x - 16 = 0
19x = 16
x = 16/19

Substitute x into equation 1 to solve for y:
y = -3(16/19) + 4
y = -48/19 + 76/19
y = 28/19

Therefore, the solution to this system of equations is x = 16/19 and y = 28/19.