[tex]\it a)\ \ \left.\begin{aligned} \it x|45 \Rightarrow x\in D_{45}\\ \\ \it 3|x \Rightarrow x\in M_3\end{aligned}\right\}\ \Rightarrow A=\{3,\ 9,\ 15,\ 45\}\\ \\ \\ \left.\begin{aligned} \it x|8 \Rightarrow x\in D_{8}\\ \\ \it x|6 \Rightarrow x\in D_6\end{aligned}\right\}\ \Rightarrow x\in D_8\cap D_6 \Rightarrow B=\{1,\ 2\}\\ \\ \\ x+3|36 \Rightarrow x+3\in\{1,\ 2,\ 3,\ 4,\ 6,\ 9,\ 12,\ 18,\ 36\}|_{-3} \stackrel{x\in\mathbb{N}}{\Longrightarrow} \\ \\ \\ \Rightarrow x\in\{0,\ 1,\ 3,\ 6,\ 9,\ 15,\ 33\}[/tex]
[tex]\it 4|x^2 \Rightarrow x=par \Rightarrow C=\{0,6\}[/tex]
[tex]\it b)\ cardA=4;\ \ \ cardB=2;\ \ \ cardC=2[/tex]
