Subtract five and two-fifths minus two and nine-tenths. Justify your steps.

5 2/5 - 2 9/10

5 4/10 - 2 9/10

4 14/10 - 2 9/10 = 2 5/10 = 2 1/2

The easier way is to use decimals.

5.4 - 2.9 = 2.5