A 63 liter mixture contains milk and water in a ratio of 4:5. then x liters of milk and y liters of water are added to the mixtu
re, resulting in a milk to water ratio of 7:5. finally , 60 liters of the mixture are drained and replaced with 60 liters of water, resulting in a milk to water ratio of 7:8. what is the value of x+y ?