ab:ba=4 rest 3
ab=4ba+3 ; ab=10a+b ; ba=10b+a
=>10a+b=4(10b+a)+3
10a+b=40b+4a+3
6a-3=39b , impartim fiecare termen la 3
2a-1=13b
b<2 (daca b ar fi 2=> 2a-1=26 , dar a este cifra )
deci, b=1 => 2a-1=13=>2a=14 =>a=7
ab=71
Verificare: 71:17=4 rest 3;
17·4+3=68+3=71 (A)
