Вычислите (15/98-17/28) : 4 целых 5/21 + (4/40-3/20) x 21 целую 3/7

(15/98 - 17/28) : 4 5/21 + (4/40 - 3/20) * 21 3/7 = - 1 5/28

выражением:

= (30/196 - 119/196) : (89/21) + (4/40 - 6/40) * (150/7) =

= (- 89/196) * (21/89) + (-2/40) * (150/7) =

= - 21/196 + (-1/20) * (150/7) =

= - 3/28 + (- 15/14) =

= - 3/28 + (- 30/28) =

= - (30+3) / 28 = - 33/28 = - 1 5/28

по действиям:

1) 15/98 - 17/28 = (15 * 2 - 17*7) / 196 = (30-119) / 196 = - 89/196

2) 4/40 - 3/20 = (4 - 3*2) / 40 = - 2/40 = - 1/20

3) - 89/196 : 4 5/21 = (- 89/196) * (21/89) = - 21/196 = - 3/28

4) - 1/20 * 21 3/7 = (-1/20) * (150/7) = - 15/14 = - 1 1/14

5) - 3/28 + (- 1 1/14) = - 3/28 + (-1 2/28) = - 1 5/28