Answer:
Mon needs 2.5 pounds of sugar and 2.5 of syrup.
Explanation:
To make 50% syrup, having 5 pounds of sugar syrup, it would be

Mon would need 2.5 pounds of sugar.
Now, Mon has 2.5 pounds of sugar, how much water does she need to make 50% syrup?

This means that Mon needs 2.5 pounds of water too.
As you can see, the easiest way to find the answer would be to divide the initial 5 pounds in to equal parts, which are 2.5, because they syrup have to 50%.
Therefore, Mon needs 2.5 pounds of sugar and 2.5 of syrup.