Okay. So you’re talking an elevation below and above sea level. It do this, let’s look for the absolute value of each number, which is the value away from 0 and is always positive. All you have to do is look at that number. That number is the distance away from 0 and if the number is negative, change it into a positive. The absolute value of 14,721 is 14,721 and the absolute value of 282 is 282. Let’s add both numbers. 14,721 + 282 = 15,003. There. The difference between those two elevations is 15,003 feet.
