1978 AHSME Problem 30

In a tennis tournament, n women and 2n men play, and each player plays exactly one match with every other player. If there are no ties and the ratio of the number of matches won by women to the number of matches won by men is 7/5, then n equals

\textbf{(A) }2\qquad \textbf{(B) }4\qquad \textbf{(C) }6\qquad \textbf{(D) }7\qquad \textbf{(E) }\text{none of these}

Full credit goes to MAA for authoring these problems. These problems were taken on the AOPS website.