get y in terms of x then substitute the expression into the other equation.
#7. y - 2x = -6 y = 2x -6 y gets substituted for 2x - 6 5x - (2x - 6) = 9 5x - 2x + 6 = 9 3x + 6 = 9 3x = 9 - 6 3x = 3 x = 1 use this to find the other one y - 2(1) = -6 y - 2 = -6 y = 2 - 6 y = -4
#8. 3y + x = 2 x = 2 - 3y substitute x for 2 - 3y in the second equation y - (2 - 3y) = -6 y - 2 + 3y = -6 4y - 2 = -6 4y = 2 - 6 4y = -4 y = -1 use this to find the other one -1 - x = -6 -x = 1 - 6 -x = -5 x = 5
