Răspuns:
a-b=7
numere de trei cifre cu produsul cifrelor 7 sunt:117,171,711
a-b=7
a+b=117
a+b+a-b=7+117
2a=124=>a=124:2=>a=62
b=117-62=>b=55
_________
a-b=7
a+b=171
a+b+a-b=171+7
2a=178=>a=178:2=>a=89
b=171-89=>b=82
__________
a-b=7
a+b=711
a+b+a-b=711+7
2a=718=>a=718:2=>a=359
b=711-359=>b=352