List and count elements

1. List the set P = {factors of 12}.
2. Given Q = {multiples of 5 less than 30}, find n(Q).
3. True or false: 7 ∈ {prime numbers}?
4. Write down ∅ as a set.
5. If ξ = {1,2,3,...,10} and A = {2,4,6,8,10}, list the elements NOT in A.

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