3456
Объяснение:
x + y = 120
0.4x = 0.6y
y = 0.4x / 0.6 = 2x/3
x + 2x/3 = 120
5x / 3 = 120
5x = 360
x = 72
y = 2*72/3 = 48
x * y = 72 * 48 = 3456
