Răspuns :

[tex]\overline{5xy}+\overline{x3y}+\overline{xy7}=\\ =500+10x+y+100x+30+y+100x+10y+7=\\ =210x+12y+537=\\ =3(70x+4y+149)=>(\overline{5xy}+\overline{x3y}+\overline{xy7})\vdots 3[/tex]