Question

Solve using substitution method.
6x-3y=18, 6x+3y=-12

Answer 1

This is what I have done so far not sure if it is right.
6x-3y=18
6x+3y=-12
12x=-12
x=-1

6(-1) -3Y=18
-6-3Y=18
+6 +6
-3y=24
/-3 /-3
y=-8

Answer 2

Using the second equation:
-12 - 6x = 3y
-4 - 2x = y

So 6x - 3(-4 - 2x) = 18
6x + 12 + 6x = 18
12x = 6
x = 1/2

Since -4 - 2x = y
- 4 - 2(1/2) = y
-4 - 1 = y
y = -5

Check your solution:
6x - 3y = 18
6(1/2) - 3(-5) = 18
3 + 15 = 18
18 = 18
Yup, it checks out. So x = 1/2 and y = -5!