Calculus (3rd Edition)

$$f'(3)=5, \quad f(3)=17.$$
Since the tangent line at $x=3,$ has the equation $$y=5x+2,$$ then $f'(3)$ is the slope, that is, $$f'(3)=5.$$ Moreover, the tangent line at $x=3$ coincides with the function itself, that is, $$f(3)=5(3)+2=15+2=17.$$