First you make the fractions have a common denominator. In this case it would be 6.
Then you have 8 3/6 - 2 4/6.
Because the number you are subtracting is greater than what you are subtracting from, you can turn the fraction into an improper fraction.
8 3/6 = 7 9/6
9/6 - 4/6 = 5/6
Then subtract the whole numbers.
7-2 = 5
Answer: 5 5/6