How do you solve 3x+4y=12 and 2x=y-6

3x + 4y = 12

2x = y-6 Rewrite this as y = 2x+6

now replace that for y in the first equation

3x + 4 (2x+6) = 12

now do all the calculations:

3x + 8x + 24 = 12

11x + 24 = 12

11x = - 12

x = - 12/11 = - 1 1/11

now substitute - 12/11 for x in the 2nd equation and solve

y = 2x+6

y = 2 (-1 1/11) + 6

y = 42/11 = 3 9/11