4. y=4x-7 ---- first equation
y=2x+9 ---- second equation
substitude first equation into second equation
4x- 7 = 2x + 9
2x = 16
x = 8 --- third equation
substitude third equation into first equation
y = 4(8) - 7
y = 25
5. 8x+2y=-2 ---- second equation
y=-5x+1 ---- first equation
substitude first equation into second equation
8x + 2(-5x+1) = - 2
8x - 10x + 2 = - 2
2x = 4
x = 2 ---- third equation
substitude third equation into first equation
y = - 5(2) + 1
y = - 9
6. y+2x=-1 ---- second equation
y-3x=-16
y = 3x - 16 ---- first equation
substitude first equation into second equation
3x - 16 + 2x = - 1
5x = 15
x = 3 --- third equation
substitude third equation into first equation
y + 2(3) = - 1
y = - 7
