Question 103010
let x = the rate of first car and x+20 =the rate of the second car.
The distance the first car travels is the product of 5x since it traveled 5 hours.  The second is 5(x+20).  The total distance they travel is 500 miles.

5x+5(x+20)=500
5x+5x+100=500
10x+100=500
10x+100-100=500-100
10x=400
x=40

So, 1st car's speed is 40 and since the second car travels 20 mph faster, its speed is 60 mph.

Good luck!