Răspuns:
a+b=631
a:b=3 rest7=>a=3b+7
3b+7+b=631
4b=631-7
b=624:4
b=156
a=3·156+7=>a=475
a : b = 3 rest 7
a + b = 631
a = 3 × b + 7
3 × b + 7 + b = 631
4 × b + 7 = 631
4 × b = 631 - 7
4 × b = 624
b = 624 : 4
b = 156
a = 3 × 156 + 7
a = 468 + 7
a = 475