2010 Pascal Problem 21

In the diagram, each of the five boxes is to contain a number. Each number in a shaded box must be the average of the number in the box to the left of it and the number in the box to the right of it. What is the value of x?

\textbf{(A)}\ 28\quad \textbf{(B)}\ 30\quad \textbf{(C)}\ 31\quad \textbf{(D)}\ 32\quad \textbf{(E)}\ 34

If there are no answer choices shown, enter a numerical answer.

Full credit to this problem is given to the CEMC, you may view all Pascal contests here.