Substitute 2x + 11 where you see y in the second equation and solve for x.
3x + 4(2x + 11) = -11
3x + 8x + 44 = -11
11x + 44 = -11
11x = -55
x = -5
Now, substitute -5 where you see x in the first equation and solve for y.
y = 2(-5) + 11
y = -10 + 11
y = 1
The answers are x = -5 and y = 1.