1.
a/b=1/5 =>a=b/5
b/c=5/3 =>c=3b/5
a/c=b/5 : 3b/5
a/c=b/5 × 5/3b
a/c=1/3
2.
2,(3)=2 întregi 3/9 = 21/9 = 7/3
1,(6)=1 întreg 6/9 = 15/9 = 5/3
a=(1/7 × 7/3 - 5/3 × 1/10)^2
a=(1/3 - 1/6)^2
a=(1/6)^2=1/36
1,25=125/100=5/4
a/x=5/4
1/36 : x = 5/4
x=1/36 : 5/4
x=1/36 × 4/5
x=5/9