WILL GIVE BRANLIEST! pls help thank u sm!! :-) u are all amazing

Express the following as a function of a single angle, cos(60) cos(-20) - sin(60) sin(-20)

Ineed in figuring out this problem.

Two cyclists 84 miles apart start riding toward each other at the samen time. one cycles 2 times as fast as the other. if they meet 4 hours later what is the speed (in miles) of the faster cyclists