Please please please help me with this

Two cyclists 84 miles apart start riding toward each other at the same. one cycles 2 times as fast as the other. if they meet 4 hours later, what is the speed (in mi/h) of the faster cyclist?

Which geometric principle is used to justify the construction below?

Answer each of the questions for the following diagram: 1. what type of angles are these? 2. solve for x. what does x equal? 3. what is the measure of the angles?