Step-by-step explanation:
3x + 5y = 21 * (-4) •••••• -12x -20y = -84 (a)
4x - 2y = -24 * (3) •••••• 12x -6y = -72 (b)
(a) + (b)
-26y = -156
y = 6
3x + 5 * 6 = 21
3x = 21 - 30
3x = -9
x = -3
