If $f(x)=2x^2+4$ for all real numbers $x$, which of the following is equal to $f(3)+f(5)?$

To find the value of $f(3)+f(5)$, find the values of $f(3)$ and $f(5)$ separately: $f(3)=2(3{)}^2+4=22$ and $f(5)=2(5{)}^2+4=54$. So $f(3)+$ $f(5)=76$. You can tell that $f(4)$ will be between 22 and 54 , so you can cross out (A). If you Ballpark (C) and (D), putting 10 or 15 in the function will give you a number bigger than 100 , and you're looking for 76, so (C) and (D) are too big. That means the answer is (B) by POE.