Explanation:
it is the other way around based on the description.
450 ml are made by mixing (diluting) 50 ml with water.
that means that of the 450 ml 50 ml are cordial, and the rest (450-50 = 400 ml) is water.
therefore, 1/9 is the fraction of cordial, but 8/9 is the fraction of water.
50/450 = 1/9
400/450 = 8/9