Explanation

The recipe calls for 2 cups of sugar, but Sarah has only 1/2 cup.

To find out how much more sugar she needs, subtract the amount she has from the amount required:

2cups - 1/2 cup = 1/2 cups - 1/2 cup = 3/2 cups

So, Sarah needs 1 1/2 cups (or 3/2 cups) more sugar.

The correct answer is: 3/2 cup