1) a-b=18/5
a=7b
Inlocuimm in prima relatie.
7b-b=18/5 ->6b=18/5 | :6--->18/5 *1/6 =3/5
b=3/5
a=7a---->a=7*3/5----->a=21/5
2) a-b=16.4
b=a/3
Inlocuim: a-a/3=164/10 ; inmultim ecuatia cu 30 ----->30a-10a=492--->20a=492 |:20=>a=24,6
b=a/3--->b=24,6/3--->b=246/30-->b=8,2