Jessie is building a doghouse. For one side of the roof, she needs a board that is 7 3/4 feet long. She has a board that measure 9 1/12 feet. How much of the length does she need to cut from the board? Show your work and simply the fraction.

9 1/12 ft = 109/12

7 3/4 = 31/4

You need to give them the same denominator, so you'll need to multiply the top and bottom of 31/4 by three

109/12 - ((31*3) / (4*3)) = x

109/12 - 93/12 = x

(109-93) / 12 = x

16/12 = x

(16/4) / (12/4) = x

4/3 = x

4/3 = 1 1/3

Jessie needs to cut 1 1/3 feet off the board.