Because you know the equation for what x is, you can substitute (2y+12) for x. Your new equation would look like this;
2(2y+12)+3y=-11
Distribute the 2 into 2y+12
4y+24+3y=-11
Add 4y and 3y
7y+24=-11
Subtract 24 from both sides
7y=-35
y=-5
Now, substitute -5 in for y in the 2nd equation.
x= 2(-5)+12
x=-10+12
x=2
x=-5
y=2
Hope this helped! You can reach out to me if you have any more questions!