(-3x + 4y) - (-3x + y) = 24 - (-3)
-3x + 4y + 3x - y = 24 + 3
3y = 27
y = 27 / 3
y = 9
-3x + 9 = -3
-3x = -3 - 9
-3x = -12
x = -12 / -3
x = 4
Ответ: (4; 9)