I believe there's an error in the question since the polynom is $x^3 + 2x$ so the $x^3$ is multiplied by 1,, in that case the answer to the example is 13 and not 12(for x=4)..

or have i got the question wrong?

In case I am not wrong.. are we needed to calculate even for the ones that are multyplied by 0 like in our case $x^2$ since now 0 isnt something that makes a number go away and it can change the answer if it was $-14*x^3$.. or make an exception for 0?

thanks

Question 4(A) fall 2015B