A hiker started her hike at 0.2 mi below sea level. At the end of her hike, she was 1.4 mi above sea level.

What vertical distance did she hike?

1.6 miles, because she started at - 0.2, meaning you have to add another 0.2 to the total she hiked vertically. If she'd started 0.2 above sea level, you'd have to subtract 0.2 from 1.4.