Answer:
He needs 3.75 lbs of sugar and 1.25 lbs of water.
Explanation:
Let x lbs be the amount of sugar in the syrup. Then 5-x lbs is the amount of water in this syrup.
Note
5 lbs - 100%
x lbs - 75%
Write a proportion:

Cross multiply:

So, he needs 3.75 lbs of sugar and 5 - 3.75 = 1.25 lbs of water.