1. Сначала решим все выражения.
1)
(13/18 + 1/7) + 5/18 = (91/126 + 18/126) + 35/126 = 109/126 + 35/126 = 144/126 = 1 1/7
2)
(5/16 + 1/14) + 11/16 = (70/224 + 16/224) + 154/224 = 86/224 + 154/224 = 240/224 = 1 1/14
3)
2/5 + (1/18 + 3/5) = 36/90 + (5/90 + 54/90) = 36/90 + 59/90 = 95/90 = 1 1/18
4)
3/17 + (1/14 + 14/17) = 42/238 + (17/238 + 196/238) = 42/238 + 213/238 = 255/238 = 1 1/14
2. Теперь приводим к общему знаменателю.
1 1/7 = 8/7 = 16/14 = 288/252
1 1/14 = 15/14 = 270/252
1 1/18 = 19/18 = 266/252
1 1/14 = 15/14 = 270/252
ответ: 2/5+(1/18+3/5)
60÷25%=240
незнаю ли верно