Mia will use one of these boards for the length of the shelter. She knows she wants the length of the shelter to measure 3.25 feet. She will use a different board for the width of the shelter. The width of the shelter will be shorter than the length. Mia needs to cut the third board to match the width of the shelter. How many feet of board will she need to cut off the existing board to reach this goal?
Since Mia wants the width of the shelter to be shorter than the length, we can assume that she wants it to be shorter by a certain amount. Let's represent this amount by x.
Therefore, the length of the board that Mia needs to cut off is 3.25 - x feet.