Answer:
$83.97
Explanation:
Let's find the total thickness of all 42 books first. To do this, we do 42 * 1.75 = 73.5 inches. We know that each shelf is 3 feet long, but we want to convert to the same unit so that it's easier to calculate, so each shelf is 3 * 12 = 36 inches long. Now, to find the number of shelves needed, we'll do total thickness/length of each shelf which is 73.5 / 36, or 2.04. Our answer has to be an integer (because you can't have half of a shelf), so do we round up or down? Well, if we rounded down, then there wouldn't be enough room for all the books, so we round up to 3 shelves instead. Because each shelf is $27.99, the price for 3 will be 27.99 * 3 = $83.97. Hope this helps!