Which piecewise relation defines a function?

Quick translate "x is 12 units from 20" into an equation. what are the values of x being described? if you can answer any of my other questions that'd be great too

Given: and prove: what is the missing reason in the proof? given transitive property alternate interior angles theorem converse alternate interior angles theorem

Tom travels between the two mile markers shown and then finds his average speed in miles per hour. select the three equations that represent this situation.