Solve the system using substitution and describe your steps.
x=y-3
2x+y=12

X = y - 3 (equation 1)
2x + y = 12 (equation 2)

Substitute equation 1 into equation 2, replacing every x value with equation 1

2(y - 3) + y = 12

Now, distribute the 2 inside the brackets and simplify.
2y - 6 + y = 12
3y = 18
y = 6 (divided both sides by 3)

Substitute y back into equation 1 to find x.
x = 6 - 3
x = 3

Verify that these are correct by substituting them into equation 2.
2(3) + 6 = 6 + 6 = 12

Therefore, x = 3 and y = 6