Question

How do I solve this system using substitution: y = x - 7 ; 2x + y = 8

Answer 1

y=x-7
2x+y=8
2x+x-7=8
3x=15
x=15/3
x=5
y=x-7
y=5-7
y=-2

x=5
y=-2

Answer 2

y = x - 7
2x + y = 8

2x + (x - 7) = 8
2x + x - 7 = 8
3x - 7 = 8
+ 7 + 7
3x = 15
3 3
x = 5
y = x - 7
y = 5 - 7
y = -2
(x, y) = (5, -2)