a) 0,3=3/10
1/3/10=1×10/3=10/3
1/2-2/3×3/10=1/2-1/5 amplificãm pe 1/2 cu 5 si pe 1/5 cu 2
5-2/10=3/10
b) 4,2=42/10=21/5
1/21/5=1×5/21=5/21
4/5×5/4-1/2×5/21=1-5/42 amplificam pe 1 cu 42
42-5/42=39/42=13/14
c) 0,57=57/100
6×3/4-5+57/100=9/2-5+57/100 amplificãm pe 9/2 cu 50 si pe 5 cu 100
450-100+57/100=350+57/100=407/100