Evaluating a Function In Exercises $21-32$ , evaluate
(if possible) the function at each specified value of the
independent variable and simplify.
$$
\begin{array}{l}{f(x)=2 x-3} \\ {\text { (a) } f(1) \quad \text { (b) } f(-3) \quad \text { (c) } f(x-1)}\end{array}
$$