Find Kayla's speed

Question

Kayla and Bill left Perry's house at the
same time. They traveled in opposite
directions. Bill traveled 59.1 mph faster
than Kayla. After five hours they were
504.5 mi. apart. 

Answer 1

Let K = Kayla's speed  

 

Then Bill's speed = K + 59.1  

 

Since they are traveling in opposite directions, the distance between them is increasing at a rate equal to the sum of their speeds, that is  

 

D = (K + (K + 59.1)) * T  

 

Plug in 504.5 mi. for D and 5 hours for T and solve for K.