64. One glass of coffee was poured into a cup, and then a quarter glass of milk from a glass filled with milk was added to this cup. After thoroughly mixing the contents of the cup, it was topped up from the glass of milk. How much milk and how much coffee is left in the cup?
64. When a quarter of a cup of milk was added to the cup of coffee already in the mug, the mug then contained $\frac{5}{4}$ cups of coffee with milk. In this case, the milk constitutes 1 part, and the coffee - 4 such parts. To top up the cup with milk, one needs to pour out a quarter of a cup of the contents of the mug. After this, there will be one cup of coffee with milk left in the mug. The ratio of coffee to milk in the mug has not changed, so there is $\frac{4}{5}$ of a cup of coffee left, and $\frac{1}{5}$ of a cup of milk.