Let [math]
  1. How many subsets are there of cardinality 4?
    (Note: you can enter “C(n,k)” for [math])
  2. How many subsets of cardinality 4 have [math] as a subset?
  3. How many subsets of cardinality 4 contain at least one odd number?
  4. How many subsets of cardinality 4 contain exactly one even number?

Solution