If you know that there are 21 members and 13 are females, if you subtract 13 from 21, you will get 8. There are 8 females in the gardening club.
Now you have to figure out the ratio to females to all club members. You already know that there are 8 females and 21 club members. The ratio would be 8:21.
I hope you found this helpful :)
646/3=x
To check it: x*3 should =646
