Answer:
Juan does not have enough lumber to make the five shelves.
Step-by-step explanation:
Let assume that:
If Juan bought a piece of lumber that is 18 feet long.
and the bookcase will have = 5 shelves
Also, the length of each bookcase = 2 1/2 long = 2.5 long
Then the amount required for the five shelves = 5 × 2.5
= 12.5 feet long
Therefore, we can say Juan does not have enough lumber to make the five shelves.
Hence, he will need an addition of: (18 - 12.5) feet = 5.5 feet piece of lumber