7a5 divizibil cu 3 => 7+5+a=M3
12+a={12,15,18,21}
a={0,3,6,9}
7a5={705,735,765,795}
4a8a divizibil cu 3=>4+8+2a=M3
12+2a={12,18,24,30}
2a={0,6,12,18}
a={0,3,6,9}
4a8a={4080,4383,4686,4989}
a45a divizibil cu 3 => 4+5+2a=M3
9+2a={9,15,21,27}
2a={0,6,12,18}, 0 nu convine
a={3,6,9}
a45a={3453,6456,9459}