ab5 : ba = 5 rest 25
ab5 = 5 × ba + 25 (conform T.I.R)
100×a + 10×b + 5 = 50b + 5×a + 25
95×a = 40×b + 20 |:5
19 × a = 8×b + 4
pentru b = 9
19×a = 8×9 + 4
19×a = 76
a = 76 : 19
a = 4
deci, ab = 49 (numarul cautat)
Verificam:
495 : 94 = 5 rest 25
495 = 94 × 5 + 25
495 = 470 + 25
495 = 495
