Răspuns :
a=2+b
(2+b+b)/2=9
2+2b=9×2
2+2b=18
2b=18-2
2b=16
b=16:2
b=8
a=2+8
a=10
Verificare: (10+8)/2=18/2=9
(2+b+b)/2=9
2+2b=9×2
2+2b=18
2b=18-2
2b=16
b=16:2
b=8
a=2+8
a=10
Verificare: (10+8)/2=18/2=9