x + y = 20
x - y = 4
y = -x + 20
x -(-x + 20) = 4
x + x - 20 = 4
2x = 24
x = 12
y = -12 + 20
y = 8
ответ: (12; 8)
x + y = 20
x - y = 4
y = -x + 20
x - y = 4
x -(-x + 20) = 4
x + x - 20 = 4
2x = 24
x = 12
y = -12 + 20
y = 8
ответ: (12; 8)