30:(5-21//26*5 1//5:1 1//5)=30:(5-21//26*26//5:1 1//5)=30:(5-21//26*5.2:1 1//5)=30:(5-4.2:1 1//5)=30:(5-4.2:6//5)=30:(5-4.2:1.2)=30:(5-3.5)=30:1.5=20

1. 5 1//5=26//5

2. 26//5=5.2

3. (21//26)*5.2=4.2

4. 1 1//5=6//5

5. 6//5=1.2

6. 4.2:1.2=3.5

7. 5-3.5=1.5

8. 30:1.5=20

// - черта дроби