ab5=ba x 5 +25
100a+10b+5=5(a+10b)+25
95a-40b=20
19a-8b=4
19a=8b+4, rezulta ca 19a=nr.par
a=2, 38=8b+4, b=34/8=17/4, nu e solutie
a=4, 76=8b+4, b=9, solutie
a=6, 114=8b+4, b=110/8=55/4, nu e solutie
a=8, 152=8b+4, b=148/8=37/2, nu e solutie
a=4 si b=9
Verificare:
ab5=5 x ba + 25
495=5x94+25
495=470+25, adevarat