Answer: |a-c| which is choice 2
Explanation:
Let's attach numbers to each variable
a = 1000
c = 700
If we start off at 1000 ft in the air, then go to 700 ft, then we moved 100 - 700 = 300 ft, which is the change in height.
Going from 700 back to 1000 ft is the same change in height, just the opposite direction. Note how 700 - 1000 = -300. Using absolute value will ensure the result is positive, so, |700 - 1000| = | -300 | = 300.
