The correct answer is Choice D.
Substitute $x=3$ into the given function to find $f(3)$.
Choice A is incorrect and may be the result of finding the value of $f(1)$, not $f(3)$.
Choice B is incorrect and may be the result of miscalculating $f(3)$ as $7+3+2$, not $7(3)+2$.
Choice C is incorrect and may be the result of miscalculating $f(3)$ as $7+2(3)$, not $7(3)+2$.
✨ Expert's Tip ✨
Another method is to plot the graph of the given function and read the value of the function at $x=3$.