1) 13-(6.6-2 8//15)*3=13-(6.6-38//15)*3=13-61//15*3=13-12.2=0.8

2 8//15=38//15

6.6-38//15=61/15

61/15*3=12.2

13-12.2=0.8

2) 50-(3 3//4+6.5)/0.25=50-(15//4+6.5)/0.25=50-(3.75+6.5)/0.25=50-10.25/0.25=50-41=9

3 3//4=15//4

15//4=3.75

3.75+6.5=10.25

10.25/0.25=41

50-41=9

// - черта дроби