Assuming the two triangles are similar, find the towers height from the given measurements below

Which expression is equivalent to 2^4y^3

Ineed if you could explain and give me the answer you! this needs done

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?