1)1 1/5*(3/4-1/3)=1/2

3/4-1/3=9/12-4/12=5/12

1 1/5*5/12=6/5*5/12=1/2

2)2:(15/16-1/4)=2 10/12

15/16-1/4=15/16-4/16=11/16

2:11/16=2*16/11=32/11=2 10/11

3)(1/3+2/9):9/10-2/5=88/405

1/3+2/9=3/9+2/9=5/9

5/9:9/10=5/9*10/9=50/81

50/81-2/5=250/405-162/405=88/405