There were 336 red and blue pens in a box. ¼ of them were red. After some red pens were removed, the number of remaining red pens was 1/7 of the total remaining pens. What fraction of the total pens was removed?
1/4 * 336 = 84
84-x = 1/7 (336-x)
x = 42
42/(336-42) = ____