3ab | 2 => b={0,2,4,6,8}
1) b=0 => 3ab={310,320,330,340,350,360,370,380,390}
2)b=2 =>3ab= {312,322,332,342,352,362,372,382,392}
3)b=4 => 3ab={314,324,334,344,354,364,374,384,394}
4)b=6 => 3ab={316,326,336,346,356,366,376,386,396}
5)b=8 => 3ab={318,328,338,348,358,368,378,388,398}
in total sunt 9x5=45 de numere
