21/25 as a percent. Well, I would change the 25 so its 100. But don't forget to also multiply the top and bottom by the same number.
So multiply 21/25 by 4/4= 84/100. Since a percentage is out of a whole, you just take 84 and move it by itself: 84%
So 21/25 as a percent I think is 84%
Hope this helps! :D