Because basketball was used first and football second you would put basketballs number first, which is 2. Then you would use footballs number which is 4. It asked what is the ratio so it would be 2 to 4 because your explaining the value of each other towards each other, other ways to write this is 2:4, 2/4, or like the first one 2 to 4.
Hoped this helped! :)