The reeds are moving across the country. mr. reed leaves 4.5 hours before mrs. reed. if he averages 70 mph and she averages 85 mph, how long will it take mrs. reed to overtake mr. reed?

I was originally going to graph the two equations, but I don't have graph paper so I set the equations equal to each other.
so Mr.Reeds equation is: y=70x+4.5 and Mrs.Reeds equation is: y=85x
so if I set these equal to each other I would minus the 70x from both sides leaving me with 15x = 4.5. Now since that's done I would divide everything by 15 which will cause me to get a fraction. So once that's done I would be left with x=3/10. I hope this helped!