Solve each system by substitution

Question

Solve each system by substitutional

y=5x-7

y=-6x-7

Solve each system by substitutional

y=3x+12

y=-3x-18

Solve each system by substitutional

y=6x-4

y=-3x+5

Answer 1

first: x=0, y=-7 (0,-7) subtract 1st from 2nd equation to get 0 = x, plug that into either equation to get y=-7

2nd: add the equations to get 2y = 30, y=15 x=1 (1,15)

3rd (1/9, 14/3)