12,96 + 0,62x + 1/5x = x
0,62x + 1/5x - x = -12,96
(31/50)х + (10/50)х - х = -12,96
(41/50)х - х = -12,96
(-9/50)х = -12,96
-0,18х = - 12,96
х = -12,96 ÷ (-0,18)
х = 72
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Проверка:
12,96 + 0,62×72 + (1/5)×72 = 72
12,96 + 44,64 + 14 целых 2/5 = 72
57,6 + 14,4 = 72
72 = 72