Example 4 and 5

Example 4
Given the function $f:x\mapsto 3x+2$  , find the value of
(a) $f(2)$
(b) $f(-5)$
(c) $f\left(\frac{1}{3}\right)$

Example 5
If $f(x)=x^2+3x+2$  , express each of the following in terms of x:
(a) $f(2x)$
(b) $f(3x+1)$
(c) $f(x^2)$