A) 8421ft.
All you have to do to find the difference is add 427 to 8848.
To better explain, imagine -427 and 8,848 on a number line. The difference is the amount of numbers between 427 and 8,848. You would subtract 8,848 to reach 0, and you would add 427 to -427 to get to get to 0. So it took you 8421 numbers to reach 0 from both sides.
