how many feet is the river

Question

Tasha went diving in the river with friends who had a metal detector. She descended 15 feet down to the bottom and then ascended 4 feet on the line to help her friend with the detector. They then swam at that depth to a ledge that was 2 feet below them, where they located a lost ring with the detector. How far down was the ring?

 

Group of answer choices

-13 feet

-17 feet

13 feet

-2 feet

Answer 1

-15+4-2 = -13 feet

although the question is slightly ambiguous. It asks how far down.

-13 indicates down already. +13 is how far down they went. Still -13 looks like the more likely answer expected.