First convert 2 1/2 in to a improper fraction. To do so, multiply 2 by 2 and add 1 then put that answer above to. It should look like 5/2. Then to subtract both denominators must be the same. So multiply the numerator and denominator of 5/2 by 3 and get 15/6. Then do the same thing to 1/3 but with 2. It should look like 2/6. Now subtract. 15/6-2/6=13/6=2 1/6