The book shelf is 2 2/4 ft long and you are filling 2/3 of it. To find out how much of the shelf we're actually filling. To find this we would have to multiply 2 2/4 by 2/3.
For the sake of the problem I converted 2 2/4 into an improper fraction which is 11/4. You multiply the numbers across then you get 22/12 which reduced is 5/6.
Now that we know we're filling 5/6 feet in the shelf, we need to know how many books we're filling in this space. since all the books are 3/8 wide, we divide 5/6 by 3/8 then the answer is 40/18. To simplify, we divide 40 by 18 we get 2.2, and rounded the answer is two.
So you can fit two books in the book shelf