9/56 - (7/15 - 5/12)*(3/14 + 1/2) = 1/8
7
15
- 5
12
= 7·4
15·4
- 5·5
12·5
= 28
60
- 25
60
= 28 - 25
60
= 3
60
= 1 · 3
20 · 3
= 1
20
= 0.05
3
14
+ 1
2
= 3 · 1
14 · 1
+ 1 · 7
2 · 7
= 3
14
+ 7
14
= 3 + 7
14
= 10
14
= 5 · 2
7 · 2
= 5
7
≈ 0.7142857142857143
1
20
× 5
7
= 1·5
20·7
= 5
140
= 1 · 5
28 · 5
= 1
28
≈ 0.03571428571428571
9
56
- 1
28
= 9·1
56·1
- 1·2
28·2
= 9
56
- 2
56
= 9 - 2
56
= 7
56
= 1 · 7
8 · 7
= 1
8
= 0.125
1100:25=44(м/мин)...
Если конечно правильно.