Crystal buys headphones that are on sale with a 40% discount. If Crystal pays $24 for the headphones with the discount, what is the full price of the headphones?

Let X be the full price of the headphones.

The discount on the headphones is X * 40% = $24
The full price of the headphones is X = $24 * 100% / 40% = $<<24*100/40=60>>60. Answer: \boxed{60}.