$A$ function $f$ is defined by $f(x) = 2x - 5$. Find the value of $f(7)$.

If $Q$ denotes the set of all rational numbers and $f\left(\frac{p}{q}\right)=\sqrt{p^2-q^2}$ for any $\frac{p}{q} \in Q$, then observe the following statements.
$I$. $f\left(\frac{p}{q}\right)$ is real for each $\frac{p}{q} \in Q$.
$II$. $f\left(\frac{p}{q}\right)$ is a complex number for each $\frac{p}{q} \in Q$.
Which of the following is correct?

Examine the following relation and state whether it is a function or not,giving reasons:
$R = \{(1, 2), (2, 3), (3, 4), (4, 5), (5, 6), (6, 7)\}$

$A$ function $f$ is defined by $f(x) = 2x - 5$. Find the values of $f(0)$,$f(7)$,and $f(-3)$.

Which of the following is $NOT$ a function?

The function $t$,which maps temperature in degree Celsius into temperature in degree Fahrenheit,is defined by $t(C) = \frac{9C}{5} + 32$. Find the value of $C$ when $t(C) = 212$.