Giles is searching for a sock and discovers that he has 10 socks for every 5 pairs of shoes. If he has 20 socks, how many pairs of shoes does he have? Show your work. Explain.

The answer is 10 pairs of shoes.
The first ratio is 10:5. 10 socks per 5 pairs of shoes. You have 20 socks now instead of 10. You just double the ratio. 20 socks per 10 pairs of shoes. 20:10.