Răspuns :
a/b=7/5 =>a=7b/5
a-b=42
7b/5-b=42
7b-5b=210
2b=210 =>b=105
a=147
a-b=42
7b/5-b=42
7b-5b=210
2b=210 =>b=105
a=147
a/b=7/5→a/7=b/5=k=→a=7k si b=5k
a-b=42
7k-5k=42
2k=42
k=21
a=7•21
a=147
b=5•21
b=105
a-b=42
7k-5k=42
2k=42
k=21
a=7•21
a=147
b=5•21
b=105