I think the one you chose is correct but I am not sure tho
Number of books = 42 / 5/8 (Note 3 1/2 feet = 42 ins.)
= 42 * 8/5 = 336 / 5 = 67.2
67 books will fit on the shelf.
First u do a squared +b squared =c squared aka pythagorean theorem then so u already have c squared so you would do 5x5=25 and 13x13=169 so then the equation would be 25+?=169 then do 169-25 which equals 144 and then do the square root of that which is 12 THE ANSWER IS 12
