We can do this by simply checking each multiple of the ratio.
2:3= 6 members
4:6= 10 members
6:9= 15 members
8:12= 20 members; not enough because there's supposedly more than 20.
10:15= 25 members; let's check if any other values would work.
12:18= 30 members; too much.
So, there are 25 members in the checkers club (10 boys and 15 girls).
