There's one way you can go through with this that I know of: create an equivalent fraction with 100 as the denominator. For the first fraction, 9/10 is equal to 90/100, making the percent 90%. For the second, 5 times 20 is 100, and you gotta do the same to the bottom and the top, so 4 times 20 is 80, making the percent 80%. The third 20 times 5 is 100, and 17 times 5 is 85, making the percent 85%.
9/10= 90%
4/5=80%
17/20=85%