Răspuns :
1b1, 2b2, 3b3, 4b4, 5b5, 6b6, 7b7, 8b8, 9b9...... b €{0, 1, 2, 3, 4, 5, 6, 7, 8, 9} => sunt 10*9=90 variante
a=c
a={1,2,3,4,5,6,7,8,9}-------9 valori in total pt. a si pt. c
b={0,1,2,3,4,5,6,7,8,9)------10 valori pt. b
9*10=90-------90 de nr.
a={1,2,3,4,5,6,7,8,9}-------9 valori in total pt. a si pt. c
b={0,1,2,3,4,5,6,7,8,9)------10 valori pt. b
9*10=90-------90 de nr.