Найдите значение выражения, избирая удобный порядок вычислений. 1) (7(5/19) + 3(7/24))

1) (7(5/19) + 3(7/24)) - 4(5/19) = (7(5/19) - 4(5/19)) + 3(7/24) = 3 + 3(7/24) = 6(7/24).
2) (13(2/17) + 6(12/35)) - 5(12/35) = 13(2/17) + (6(12/35) - 5(12/35)) = 13(2/17) + 1 = 14(2/17).
3) 12(11/21) - (3(2/13) + 8(11/21)) = (12(11/21) - 8(11/21)) - 3(2/3) = 4 - 3(2/13) = 11/13.
4) 20(21/43) - (9(21/43) + 2(15/37)) = (20(21/43) - 9(21/43)) - 2(15/37) = 11 - 2(15/37) = 8(22/37).