algebra
posted by anonymous .
At 9AM, two cars started from the same town and traveled north on the same road. One car averaged 45 miles per hour, and the other car averaged 40 miles per hour. In how many hours were the cars 30 miles apart?

The distance between them increases at a rate of 5 miles per hour.
Using that relative rate r,
r t = 5 t = 30
t = 6 hours 
Follow the example of the problem I solved for you two posting below this.
The two problems are very similar.
Let me know what you got. 
i don't get how to start on this one since it doesn't give how far apart the towns are. Well, there;s only one town whatdo i do???

You don't have to know that, you know they are 30 miles apart.
So if you let the time be t hours, then the faster has traveled 45t miles, and the slower has traveled 40 t miles
The difference in the distance traveled is 30 miles, so....
45t  40t = 30
5t=30
notice we now have the same equation that drwls obtained by simple common sense.