To subtract fractions with different denominators (in this problem they are 10 and 5), you have to find the least common denominator or LCD (10). Then you have to multiply the numerator and the denominator of 4/5 by 2 to turn the denominator into the LCD (10).
1. So 2 4/5 turns into 2 8/10
2. Then subtract 2 8/10 from 5 3/10 to get the answer 2 1/2
