Sets

Given, $$\xi$$ $$=$$ {Natural numbers between $$25$$ and $$45$$}; $$A =$$ {even numbers} and $$B$$ {multiples of $$3$$}. Find :
State which of the following sets are empty and which are not?
Set of odd natural numbers divisible by $$2$$
Let $$A=\{1,-1\}$$. Then find $$A\times A$$.
Describe the following sets in Roster form:
(i) {x/x is a letter of the word 'MARRIAGE'}
(ii) {x/x is an integer and $$- \frac{1}{2} < x < \frac{9}{2}$$}
(iii) {x/x $$=$$2n,x $$ \subset $$ N}
If P = {$$x$$ : $$x\,\,\epsilon\,\, W$$ and $$4 \leq x \leq 8$$} and Q = {$$x$$ : $$x \,\,\epsilon\,\, N$$ and $$x < 6$$}.