15 целых / (2/5 + 1/15 + 4/25 ) =
15 / (2/5 + 1/15 + 4/25) = 15 / (30/75 + 5/75 + 12/75) = 15 / 47/75 = (15 * 75) / 47 = 1125 /47= 23 44/47