1. 3,9*0,7 = 2,73

2,73*4,8 = 13,104

13,104*0,03 = 0,39312

0,91*5,4 = 4,914

4,914*0,032 = 0,157248

0,39312 : 0,157248 = 2,5

2. 3 1/3 : 10 = 10/3 : 1/10 = 1/3

2 1/6 : 3 25/100 = 13/6 : 325/100 = 13/6*100/325 = 1300/1950 = 130/195 = 26/39

1/3 + 26/39 = 13/39 + 26/39 = 39/39 = 1

1 : 125/100 = 1*100/25 = 4

2/13 *52/10 = 1/13*52/5 = 1*4/5 = 4/5

3*2/13 = 3/1*2/13 = 6/13

48/10*2/13 = 96/130

4/5 + 6/13 = (52+30)/65 = 82/65

82/65 + 96/130 = 260/130 = 2

4/2 = 2