(5 1/4-4 21/40):1 9/20-(7 1/5-6 7/8):3/4=
3/4:5/6+1:1 1/9-2 1/2×2/5=

Пошаговое объяснение:

1) 5 1/4-4 21/40=5 10/40-4 21/40=29/40

29/40:1 9/20=29/40*20/29=1/2

7 1/5-6 7/8=7 8/40-6 35/40=13/40

13/40:3/4=13/40*4/3=13/30

1/2-13/30=15/30-13/30=2/30=1/15

2) 3/4:5/6=3/4*6/5=9/10

1:1 1/9=1*9/10=9/10

2 1/2×2/5==5/2*2/5=1

9/10+9/10=18/10=1 4/5

1 4/5-1=4/5

Пошаговое объяснение:

1 пример:

1) 5. 1/4 - 4. 21/40 =

5. 10/40 - 4. 21/40 =

4. 50/40 - 4. 21/40 =

29/40

2) 29/40 : 1. 9/20 =

29/40 : 29/20 = 29/40 * 20/29 = 20/40 = 1/2

3) 7. 1/5 - 6. 7/8 =

7. 8/40 - 6. 35/40 =

6. 48/40 - 6. 35/40 =

13/40

4) 13/40 : 3/4 = 13/40 * 4/3 = 13/10 * 1/3 = 13/30

5) 1/2 - 13/30 = 15/30 - 13/30 = 2/30 = 1/15

ответ: 1/15

2 пример:

1) 3/4 : 5/6 = 3/4 * 6/5 =

18/20 = 9/10

2) 1 : 1. 1/9 = 1 : 10/9 =

1 * 9/10 = 9/10

3) 2. 1/2 * 2/5 = 5/2 * 2/5 = 1

4) 9/10 + 9/10 = 18/10 = 9/5 = 1. 4/5

5) 1. 4/5 - 1 = 4/5

ответ : 4/5