# Set theory question

## Homework Statement

Assume that ##x## and ##y## are members of a set ##B##. Show that ##\{ \{x\}, \{x,y\} \} \in \mathcal{P} \mathcal{P} B##

## The Attempt at a Solution

I know that ##\{ \{x\}, \{x,y\} \} \in \mathcal{P} \mathcal{P} B## iff ##\{ \{x\}, \{x,y\} \} \subseteq \mathcal{P} B##, but I don't see where this gets me. To me it's obviously true, but I don't see how to show it.

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