Răspuns :
1. (21+43-31):a=3 2. [(80+9)+(40-3a)]:8=15 3. 6+6x[a+15x(6x2-10)]=270
(64-31) :a =3 [89+(40-3a)]:8=15 6x[a+15x(12-10)]=264
33:a=3 89+(40-3a)=120 6x(a+15x2)=264
a=33:3 40-3a=120-89 6x(a+30)=264
a=11 40-3a=31 6a+6x30=264
3a=9 6a+180=264
a=3 6a=84
a=13
(64-31) :a =3 [89+(40-3a)]:8=15 6x[a+15x(12-10)]=264
33:a=3 89+(40-3a)=120 6x(a+15x2)=264
a=33:3 40-3a=120-89 6x(a+30)=264
a=11 40-3a=31 6a+6x30=264
3a=9 6a+180=264
a=3 6a=84
a=13