$\frac{3x+29}{x+3}=\frac{3(x+3)+20}{x+3}=3+\frac{20}{x+3}\in N$$\Rightarrow x+3\in Ư(20); x+3\geq 3$$\Rightarrow x+3=4;5;10;20\Rightarrow x=1;2;7;17$
$\frac{3x+29}{x+3}=\frac{3(x+3)+20}{x+3}=3+\frac{20}{x+3}\in N$$\Rightarrow x+3\in Ư(3)\Rightarrow x+3=1;3\Rightarrow x=0$ hoặc $x=-2$ ( loại vì $x\in N)$
$\frac{3x+29}{x+3}=\frac{3(x+3)+20}{x+3}=3+\frac{20}{x+3}\in N$$\Rightarrow x+3\in Ư(
20)
; x+3\geq 3$$\Rightarrow x+3=
4;5;1
0;
20\Rightarrow x=
1;2
;7;17$