Answer:
15 cups
Explanation:
So we have a ratio, butter:sugar. This ratio is given as 3:5, or 3 parts to 5 parts. Basically, every 3 cups of butter you use, you use 5 cups of sugar.
In order to calculate this, we simply need to divide the amount of butter being used by 3, and then multiply that by 5. This way, we are figuring out how much a singular "part" is in this situation, and then multiplying that by 5 for the 5 parts sugar.
9/3 = 3
3*5 = 15
Therefore, you have 15 cups of sugar.