If Tom Bombadil's house is 12 miles east of Hobbiton and 16 miles south, what is the straight line distance (omit units)

Question

Where do I start ?

Answer 1

Put Hobbinton at the origin (0,0) on the x-y grid
then Tom's house would be (12,-16)
distance from (0,0) to (12,-16)
= √(12^2 + (-16)^2)
= √400
= 20