If $A = \{1, 2, 3, 4\}$,$B = \{3, 4, 5, 6\}$,$C = \{5, 6, 7, 8\}$,and $D = \{7, 8, 9, 10\}$,find $A \cup B$.

If $A$ and $B$ are sets,then $A \cap (B - A)$ is

If $A$ and $B$ are disjoint sets,then $n(A \cup B) = $

Let $A$ and $B$ be two sets such that $n(A) = 0.16$,$n(B) = 0.14$,and $n(A \cup B) = 0.25$. Then $n(A \cap B)$ is equal to:

$A$ class has $175$ students. The following data shows the number of students opting for one or more subjects: Mathematics $100$,Physics $70$,Chemistry $40$; Mathematics and Physics $30$,Mathematics and Chemistry $28$,Physics and Chemistry $23$; Mathematics,Physics,and Chemistry $18$. How many students have opted for Mathematics alone?

If $A, B, C$ are three sets,then $A \cap (B \cup C)$ is equal to