7x + 2y = -10
9x + 4y = -30
multiply the top equation by -2 on both sides
-14x - 4y = 20
9x + 4y = -30
add the top equation to the bottom equations
-14x - 4y = 20
-5x + 0y = -10
divide the bottom equation by -5 on both sides
-14x - 4y = 20
x + 0y = 2
The bottom equation tells us that x = 2.
multiply the bottom equation by 14 on both sides
-14x - 4y = 20
14x + 0y = 28
add the bottom equation to the top equation
0x - 4y = 48
14x + 0y = 28
divide the top equation by -4 on both sides
0x + y = -12
14x + 0y = 28
the top equation tells us that y = -12
Answer: x = 2, y = -12