Răspuns :
a+b=541
a:b=3 rest 21 => a=3*b+21
având datele de sus înlocuim
3b+21+b=541
4b+21=541
4b=541-21
4b=520
b=520:4
b=130
a=3b+21
a=3*120+21
a=390+21
a=411
Fie a,b-doua numere
a+b=541
a:b=3 rest 21
a=3b+21
3b+21+b=541
4b+21=541
4b=541-21
4b=520
b=520:4
b=130
a=3×130+21
a=390+21
a=411