3x – 2y = 15
x = 3
The two lines given by the equations above intersect in the xy-plane. What is the value of the y-coordinate of the point of intersection?

Substituting 3 for x in the first equation gives 3(3) − 2y = 15. This simplifies to 9 − 2y = 15. Subtracting 9 from both sides of 9 − 2y = 15 gives −2y = 6. Finally, dividing both sides of −2y = 6 by −2 gives y = −3.