AI Tutor
Imagine you wake up in a mountain cabin where it is a freezing −5∘F-5^\circ\text{F} outside, but by noon the sun warms everything up to +8∘F+8^\circ\text{F}.
If you just subtract 8−5=38 - 5 = 3, it feels way too small — so how many degrees did the temperature actually rise?
To find the true distance across positive and negative numbers, we need a special stop along the way.

Bridging Through Zero

Think of zero as a bridge in the exact middle of your number line.
To travel from −5-5 to +8+8, you first walk from −5-5 up to 00, which is a distance of 55 steps. Then you walk from 00 up to +8+8, which is another 88 steps.
Because distance is always positive, you simply add both hops together: 5+8=135 + 8 = 13 degrees total.
What happens if we look at heights above and below the surface of the ocean?

Elevation Above and Below Sea Level

In real-world science, sea level is set at 0 feet0\text{ feet}, heights above the water are positive, and depths below the surface are negative.
Suppose a sea turtle swims at −12 ft-12\text{ ft} while a pelican flies directly overhead at +15 ft+15\text{ ft}.