xx1 = 100x+10x+1 =110x+1
66y = 600+60+y = 660+y
xy5 = 100x+10y+5
------------------------------------
xx1 +66y+xy5 = 110x+1+660+y+100x+10y+5
xx1 +66y+xy5 = 210x +666 +11y = 3(70x+222) +11y
Daca y se divide cu 3 atunci (xx1 +66y+xy5) va fi divizibil cu 3, oricare ar fi x apartine lui N
