\(\newcommand{\pow}{\mathcal P}\)
Let [math]
  1. How many subsets of [math] are there? That is, find [math] Explain.
  2. How many subsets of [math] contain exactly 5 elements? Explain.
  3. How many subsets of [math] contain only even numbers? Explain.
  4. How many subsets of [math] contain an even number of elements? Explain.

Solution