Solve:

Plug in -3x-6 for y. Simplifying you should get  6x-6=8 solving that gives you 14/6 or 7/3 for x. Plug that back in for x in the first equation and 2.3333333333333333*3-6 = 0.9999999999999999 or 1 rounded :). Hope this helps 

$y = -3x - 6\\ -y = 3x + 6\\ 3x - y = 8\\ 3x + (3x + 6) = 8\\ 6x + 6 = 8\\ x +1 = \dfrac{4}{3}\\ x = \dfrac{1}{3}\\ y = -3(\dfrac{1}{3})-6 = -7\\ \therefore x = \dfrac{1}{3};y=-7$