Вычислите 12 1/4-(3 5/12+5 1/6) заранее .

12 1/4 - (3 5/12 + 5 1/6) = 3 2/3,

1) 3 5/12 + 5 1/6 = (3 + 5) + (5/12 + 1/6) = 8 + (5/12 + 2/12) = 8 + 7/12 = 8 7/12,
2) 12 1/4 - 8 7/12 = (11 - 8) + (1 1/4 - 7/12) = 3 + (5/4 - 7/12) = 3 + (15/12 - 7/12) = 3 + 8/12 = 3 + 2/3 = 3 2/3