How do you find a common denominator when subtracting whole numbers and fractions?

Answer 1

Find the common denominator for the fractions.

Example:

2 3/4 - 1 2/5

The common denominator is 20.

2 3/4 = 11/4 = 55/20

1 2/5 = 7/5 = 28/20

Answer 2

Thank you sooo much for your help now it all makes sence!!!! ;))

Answer 3

Please explain how i would do this.
8 1/9 - 1 6/7 =?