5.
a) a+b=43
b=a+1
2*a=42
a=42/2=21
b=21+1=22
b) a+b+c=48
b=a+1
c=a+2
3*a=48-3=65
a=45/3
a=15
b=15+1=16
c=15+2=17
c) a+b=26
b=a+2
2*a=26-2=24
a=24/2=12
b=12+2=14
d) a+b+c=57
b=a+2
c=a+4
3*a=57-6=51
a=51/3=17
b=17+2=19
c=17+4=21
6. ??? Nu inteleg intrebarile.