Sets

goals
If $A = \left \{1, 2, 3, 4\right \}$, what is the number of subsets of A with at least three elements?
Which of the following is equivalent set
(i) $A=\{2,3,5,7\}$
(ii) $B=\{a,e,i,o,u\}$
(iii) $C=\{-1,-9,-8,-7\}$
Which of the following is set
Find the smallest set $\displaystyle Y$ such that $\displaystyle Y\cup \left \{ 1, 2 \right \}=\left \{ 1, 2, 3, 5, 9 \right \}$
If $G = \{7, 8\}$ and $H = \{5, 4, 2\}$, find $\displaystyle G\times H$ and $\displaystyle H\times G$.