Question

A submarine started 9 meters below the surface of the water. It is now 1 meters below the surface. What was its change in depth?

Answer 1

so 9 meters below is -9, then you have to go up x to get 1 so 1-(-9) is 10., so it went up 10, or the change was 10 i should say

Answer 2

9 meters below the surface means it is -9 meters. 1 meter below the surface means it is -1. So its change of depth is -9 + x = -1. Add 9 to both sides to get x = 8 feet. It increased 8 feet.