If $\displaystyle f(x) = x^2-1$ and $\displaystyle g(x) = 2x+3$ then $\displaystyle gof(3)$

If $\displaystyle A = \{1, 2, 3, 4, 5\}$, $\displaystyle B = \{2, 4\}$ and $\displaystyle C = \{1, 3, 5\}$ then $\displaystyle (A - C)$$\displaystyle \times$ B is:

If $\displaystyle f(x)=x^2-5$, evaluate $\displaystyle f(3)$, $\displaystyle f(-4)$, $\displaystyle f(5)$, and $\displaystyle f(1)$.

Out of a group of $20$ teachers in a school, $10$ teach Mathematics, $\displaystyle 9$ teach Physics and $\displaystyle 7$ teach Chemistry. $\displaystyle 4$ teach Mathematics and Physics but none teach both Mathematics and Chemistry. How many teach Chemistry and Physics; how many teach only Physics?

If $\displaystyle A = \{1, 2, 3, 4, 5, 7, 8, 9\}$ and $\displaystyle B = \{2, 4, 6, 7, 9\}$ then how many proper subset of $\displaystyle A \cap B$ can be created?

The number of subsets of the set $\displaystyle \{0, 1, 2, 3\}$ is:

If $\displaystyle f(x) = x^2+x-1$ and $4f(x) = f(2x)$, then find the value of 'x'.