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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
