Answer
(a) $\frac{1}{x+3}$
(b) $\frac{x+3}{3x}$
Work Step by Step
(a) Since $h(x)=\frac{1}{x}$, replace $x$ with $x+3$ to get $h(x+3)$. $$h(x+3)=\frac{1}{x+3}$$ (b) Find $h(3)$ by inputting $x=3$ into $h(x)$. $$h(3)=\frac{1}{3}$$ Therefore, $$h(x)+h(3)=\frac{1}{x}+\frac{1}{3}=\frac{3}{3x}+\frac{x}{3x}=\frac{x+3}{3x}$$
