<u>Answer:</u>
An equation that relates the speeds of the two legs of the trip

<u>Explanation:</u>
Given, we have to use x to represent the speed on the second leg
Speed on first leg when increasing your speed by 40 mph will be (x-40)
Distance is given as 640 miles and time is calculated as

According to the question, increasing speed saved four hours
Therefore, the equation that relates the speeds of the two legs of the trip will be

y+6=1/3(x-9)
Moved all terms from left to right that doesn't contain y
Y=-6 +1/3x-3
Simplify
Y=1/3x-9
Your answer is c.
Answer: 7a -21 +28b
Step-by-step explanation: