Răspuns:
N = 12*c+19
N= numar de 3 cifre
C= 9 n=12*9+9
99+9=108
C=10. N=120+9
C=11. N=132+9
.............................
C=80. N=12*80+9
=960+9.
C=81. N=12 *81+9
=972+9
C=82. N=12 * 82+9
=984+9=993
82-8=72 numere
