Explain and answer this question, thx : ) (picture included)

The way it is described, you can determine that they live in a triangle. This means you can use Pythagorus to work out the answer.
Pythagorus is (a squared plus b squared = c squared)

12x12 is 144
16x16 is 256
144+256 is 400
The square root of 400 is 20, so the answer is 20 miles :)

Iam thinking the answer is a.) knew

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