Red letters and blue letters are used in a game. Some of the letters are X. All the other letters are Y. X Y X Y The ratio of the number of red letters to the number of blue letters is 2:5 The ratio of the number of red Xs to the number of red Ys is 1: 3 The ratio of the number of blue Xs to the number of blue Ys is 3:1 Work out what fraction of all the letters are Xs.