Mr. gengel wants to make a shelf with boards that are 1 1/3 feet long. if he has an 18 foot board, how many pieces can he cut from the big board?

Let us assume that the number of pieces that can be cut = x
Length of each shelf board = 1 1/3 feet
                                   = 4/3 feet
Total length of board available for making shelf = 18 foot
Then
4x/3 = 18
4x = 18 * 3
4x = 54
x = 54/4
   = 13 2/4
As we can see from the above deduction, 13 shelf's can be made from the 18 foot board. There will be about 2/4th of the board remaining, but that 2/4th part will be wasted as it cannot create a complete board.I hope the answer is to your satisfaction and the explanation is clear to you.

What mathematical statement is missing ? ? the answer is b

I’m pretty sure the answer is a