Let $A$ and $B$ be two subsets of $\xi=\{\mathbf{1}, \mathbf{2}, \mathbf{3},-------, \mathbf{4 4}, \mathbf{4 5}\}$ such that

$A=\{x: x$ is divisible by 3 and 4$\}$

$B=\{x: x$ is a perfect square number $\}$

Then $n(B-A)$ equals

A student needs to buy notebooks $(n)$ for a semester. Double the number of notebooks plus 5 must strictly exceed 15 , but the number of notebooks plus 10 must be no more than 22 . What is the range of notebooks they can buy?

Given the sets $A=\{1,2,3\} ; B=\{2,3,5\}$ and $C=\{4,5,6\}$ identify which of the following statement is incorrect.

If $A=\{x: x$ is the first three odd numbers $\}$

$B=\{2 x+3: 0 \leq x<5, x \in \mathbb{N}\}$, then which of the following is true