2004 Fermat Problem 17

An increasing sequence is formed so that the difference between consecutive terms is a constant. If the first four terms of this sequence are x, y, 3x+y, and x+2y+2, then the value of y-x is

\textbf{(A)}\ 2\quad \textbf{(B)}\ 3\quad \textbf{(C)}\ 4\quad \textbf{(D)}\ 5\quad \textbf{(E)}\ 6

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

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