Zoe had a board 5 and 1/4 feet long. she cut off a piece. now the board is 3 and 5/6 feet long. how long was the piece she cut off?

Well first you need to find the LCM (least common multiple) of 4 and 6 (the denominators) so that you can subtract them from each other.

4: 4,8,12,16,20
6: 6, 12, 18, 24
The LCM is 12.

Now we can subtract the two mixed numbers by turning them into improper fractions.

5 3/12 -> 27/12
3 10/12 -> 42/12

42-27=15

The fraction is 15/12, which simplifies into 1 1/4.

She cut off 1 1/4 feet of the board.