How to get this answer:
x+y = 8 solves to y = -x+8 after isolating y. You subtract x from both sides.
Plug this into the second equation and solve for x
3x + 2y = 21
3x + 2( y ) = 21
3x + 2( -x+8 ) = 21 ... replace y with -x+8
3x - 2x + 16 = 21
x + 16 = 21
x = 21-16
x = 5
Use this to find y
y = -x+8
y = -5+8
y = 3
We have x = 5 and y = 3 pair up to get the ordered pair solution (5,3)
