Answer:
1 1/4 cups.
Explanation:
This is a subtraction problem since Rob put too much sugar, and he only needed 4 1/8 cups. So:
5 3/8 - 4 1/8 = 1 2/8
Since they have the same denominators all you had to do was subtract the numerators and whole numbers; 5 - 4 = 1, and 3/8 - 1/8 = 2/8.
Now you have 1 2/8, which can be simplified.
1 2/8 = 1 1/4