Răspuns :
(a+b):2=3.09
a+b=2x3.09
a+b=6.18
a=2b
2b+b=6.18
3b=6.18
b=6.18:3
b=2.06
a=2x2.06
a=4.12
Verificare:(2.06+4.12):2=6.18:2=3.09
a+b=2x3.09
a+b=6.18
a=2b
2b+b=6.18
3b=6.18
b=6.18:3
b=2.06
a=2x2.06
a=4.12
Verificare:(2.06+4.12):2=6.18:2=3.09