You can both add and subtract fractions, but before you do, you need to fin a common denominator. This means that you have to get the bottom number the same In both fractions by multiplying. But whatever you do to the denominator, you also have to do to the numerator. For example, 4/5+2/3. you have to find a number that both the bottom numbers(denominators) can multiply into such as, in this case, 15. so now you have 4/15+2/15, but you need to do the same thing that you did to the denominator to the numerator. Since we multiplied 5 by 3 to get 15 in 4/5 then you have to multiply the 4 by 3 as well which gets 12/15. Now you have to do the same with the other fraction, since we multiplied 3 by 5 to get 2/15 we have to multiply the 2 by 5 as well which comes up to 10/15. Now you can add the fractions 12/15 and 10/15 to get 22/15 or 1-7/5. follow the same steps with subtraction.
