Steps:
1. Cups of milk McKenna having is
2. Cup of milk gave to Mark for cake is
3. As we are having different denominators, take LCD
4. We have to take LCD, by listings multiples of them
Therefore, LCD is 12
5. As the denominator is changed, the numerator also to be changed by same number by multiplying
6. We can directly subtract numerators, but we cannot subtract 9 from 8, so we have to take borrow from the whole number and add it to fraction. Then
As we gave borrow from 1 it becomes 0
7. Now subtracting, then
8. Hence the fraction is.
Hence, the remaining milk having with McKenna .