Answer :

U divide them together and u get 0.9 and that as a percent is 90%
or for this and any other problem . every percentage is out of a 100

soooo ,
20 | 100 %
10 | 50 %
5 | 25 %
1 | 5 %

SOOO

10 + 5 = 15 50 % + 25 % = 75 % , so know we know 15/20 is 75 percent

but you need 18/20 not 15/20 , so 1 equals 5 % in this problem


1+1+1 = 3 5+5+5 = 15

15 + 3 = 90 75 + 15 = 90 , 18/20 = 90%

I know its probably alot but I wanted to show you all I did , so that it could maybe help you in the future , just gotta plug in different numbers