First you have to make the numbers have the same denominator. To do so 25 turns into 125/5 and 28 1/5 turns into 141/5. Now you can subtract 125 and 141 and you get -16 then you put the 5 under so it's -16/5 and simplify th that and is you get -3 1/5. Hope that helps you . If it did please click the thanks button. If you have any questions then please ask them.