Problem Solving

A truck driver drove for 2 days. On the second day he drove 3 hours longer and at an average speed of 15 miles per hour faster than he drove on the first day. If he drove a total of 1020 miles and spent 21 hours driving during th e2 days, what was his average speed on the first day, in miles per hour?

a.25
b/30
c.35
d.40
e.45



qa is D

Here is my approach: please give explanation of where I went wrong and what I need to learn.

day 1: x time
day 2: x+3 time

together: x+x+3=21, x =9
first day drove 9 hours and second day drove 12 hours

avg speed is total distance over total time

Cannot find the rate of of speed in order to find the distance traveled for day 1. This is where I am lost! The wrong answer is to plug into r=D/t formula R=1020/21 but this gives completely wrong answer and also it is not logical because rates are different/

I tried to plug in but we are not calculating the avg rate of both days.