What are the reasons for this Geometry Proof in order of occurrence?

Ineed to know the ordered pairs for this equation i need the answer quick because it’s a timed test

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.

Cos^2x+cos^2(120°+x)+cos^2(120°-x)i need this asap. pls me