Answer :
5x + 2y = 21 ⇒ 5x + 2y = 21
-1x - 1y = -9 ⇒ 5x + 5y = 45
-3y = -24
-3 -3
y = 8
5x + 2(8) = 21
5x + 16 = 21
- 16 - 16
5x = 5
5 5
x = 1
(x, y) = (1, 8)
-1x - 1y = -9 ⇒ 5x + 5y = 45
-3y = -24
-3 -3
y = 8
5x + 2(8) = 21
5x + 16 = 21
- 16 - 16
5x = 5
5 5
x = 1
(x, y) = (1, 8)