Question 181, Given sets $A, B, C \subseteq\{1,2, \ldots, 2020\}$, and $A \subseteq C, B \subseteq C$, find the number of ordered set groups $(A, B, C)$.

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$\mathrm{C}_{2020}^{\mathrm{n}}$ ways to choose: specifically, choose the subset $\mathrm{A}$ of $\mathrm{C}$, with $2^{\mathrm{n}}$ ways to choose; then choose the subset $\mathrm{B}$ of $\mathrm{C}$, also with $2^{\mathrm{n}}$ ways to choose. Therefore, the number of ordered set groups (A., B, C) is $\mathrm{E}_{\mathrm{n}=0}^{2020} \mathrm{C}_{2020}^{\mathrm{n}} \cdot 2^{\mathrm{n}} \cdot 2^{\mathrm{n}}=5^{2020}$.

Solution method two: Let the set $S=\{1,2, \ldots, 2020\}$. As shown in the Venn diagram below, divide the set $S$ into 5 parts, each element of $S$ is in exactly one part, so the number of ordered set groups $(A, B, C)$ that meet the conditions is $5^{2020}$.