Answer:
(-9,-6)
Step-by-step explanation:
Since both equations are equal to y, they are equal to each other, so substitute for y by setting the equation as x+3=2x+12 and solve for x.
x+3=2x+12, subtract x from both sides and 12 from both sides.
-9=x
Then substitute -9 for x in either equation to solve for y
y=-9+3
y=-6