Answer:
13015.5 feet
Explanation:
Juan is walking up a hill at 13034 feet above sea level
So, Above sea level means +ve
So, Height of hill above sea level = +13034 feet
Base of hill is below 18.5 feet below sea level
So, Height of hill below sea level = -18.5 feet
The vertical distance that the pebble fell from top = +13034 feet -18.5 feet =13015.5 feet
Hence The vertical distance that the pebble fell is 13015.5 feet