Use substitution to find the x-coordinate of the solution to each system.
7) -x + 5y = 19
y=-2x + 6
a-2 b) 2
c) 1 d) -1
8) -8x + 5y = -20
y=-3x + 19
a) -6 b) -4
c) 4 d) 5
9) 4x - 6y= 12
y = -2x - 10
a) 3
b) 7
c) infinite number of solutions
d) -3
10) y = x + 10
| 3x - y=-18
a) 4 b)-6
c) 8 d) -8