Найдите значение выражения (1-3/4) * (4/5-3/4); 14 * (1/2+1/3+1/4); 1/3*6/7-1/7*3/4

(1 - 3/4) * (4/5 - 3/4) =

= 1/4 * (16/20 - 15/20) =

= 1/4 * 1/20 = 1/80

14 * (1/2 + 1/3 + 1/4) =

= 14 * (6/12 + 4/12 + 3/12) =

= 14/1 * 13/12 =

= (7 * 13) / (1 * 6) = 91/6 =

= 15 целых 1/6

1/3 * 6/7 - 1/7 * 3/4 =

= 2/7 - 3/28 =

= 8/28 - 3/28 =

= 5/28