After 4 years the rate would have happened 4 times making the initial deposit increase 10%. 10% of 25000 is 2500. So 25000 plus 2500 is $27500.
5 2/3 would be 3 times 5 +2 think of it as starting the letter C from the bottom to the top multiply the bottom and middle add the top
If you do that you should get 17/3