6 класс. Найдите значения выражения: 1) 4/5 + 4/7 (7

Расставим деяния:

     3        2             1

4/5 + 4/7 * (7 11/12 - 5 7/9) = 1 7/9;

1) 7 11/12 - 5 7/9 = (12 * 7 + 11 / 12) - (9 * 5 + 7 / 9) = 95/12 - 52/9 = (95 * 3 /12 * 3) - 

- (52 * 4 / 9 * 4) = 285/36 - 208/36 = 77/36;

2) 4/7 * 77/36 = 4 * 77 / 7 * 36 = 308/252 = 77/63;

3) 4/5 + 77/63 = 4 * 63 / 5 * 63 + 77 * 5 /63 * 5 = 252/315 + 308/315 = 560/315 = 16/9 = 

= 1 7/9;

       1         3               2

(4/5 + 4/7) * (7 11/12 - 5 7/9) = 2 42/45;

1) 4/5 + 4/7 = (4 * 7 / 5 * 7) + (4 * 5 / 7 * 5) = 28/35 + 20/35 = 48/35;

2) 7 11/12 - 5 7/9 = 95/12 - 52/9 = (95 * 3 / 12 * 3) - (52 * 4 / 9 * 4) = 285/36 - 208/36 =

= 77/36;

3) 48/35 * 77/36 = 12/5 * 11/9 = 132/45 = 2 42/45.