a/b=k, b≠0
1. a=kb
a. a=0,1(6)·1,(6)=(16-1)/90 · (16-1)/9=1/6·5/3=5/18
b. a=6(a-3)=6a-18
2. b=a/k
a. b=8/3=2,(6)
b. b=3,8/0,(19) =3,8:0,(19)=38/10·99/19=2/10 ·99 (am simplificat 38 si 19 cu 19)= 99/5
c. b=0,(4)/0,72=4/9:0,72=4/9:72/100=4/9·100/72=1/9·50/9=50/81
d. b=a/(2005·a)=1/2005 daca a≠0