Use the Pythagorean Theorem to determine how far the horizon line is from Felix when he is in the balloon.
(In 2012, Felix Baumgartner jumped out of a balloon that was at an elevation of 127,851 feet above the surface. The radius of the Earth is approximately 3,959 miles. )

Step-by-step explanation:

First, make sure all the units are the same. One is given in feet and the other is given in miles.

Let's convert everything to feet.

There are 5,280 feet in one mile.

So 3,959 times 5,280 is 2,090,3520

The horizon line will form a right angle so, the 2,090,3520 and the 127,851 can be used in the Pythagorean Theorem

2,090,3520^2 + 127,851^2

436,957,148,400,000 + 16,345,878,200

Then square root that answer to get

20,903,910.98 feet