7/15-3/40= 56/120-9/120=47/120
0,7=7/10
47/120 :7/10=47/120*10/7=7/12
2,4=24/10=12/5
12/5*1/3=4/5
4/5-3=4/5-15/5= -11/5
-11/5*5/11= -1
7/12:(-1)= -7/12
3/4-1 2/3=3/4-5/3=9/12-20/12= -11/20
1 5/6:(-11/20)= -11/6*20/11= -10/3
0,75=75/100=3/4
4/9-5/12=16/36-15/36=1/36
1/36+3/4=1/36+27/36=28/36
28/36*3/7=4/12=1/3
-10/3:1/3= -10/3*3/1= -10
-7/12*(-10)=35/6=5 5/6