SOLUTION: two cars (car 1 and car 2) are driving down the highway. Car 1 is moving at 60 miles per hour. Car 2 is driving at 70 miles per hour . Car 1 is starting 40 miles ahead of car 2 .Ho

Without algebra in your head:
For car 2 to make up the 40 mile distance at an approach rate of 70-60 or 10mph
will of course take 4 hours.

By algebra:  
Make this chart:

         Distance     Rate    Time
Car 1                           
Car 2                           

Let the time for both be x hours:

         Distance     Rate    Time
Car 1                           x
Car 2                           x

Fill in the given rates (speeds):

         Distance     Rate    Time
Car 1                  60       x
Car 2                  70       x

Use Distance = rate × time to fill in the
distances:


         Distance     Rate    Time
Car 1      60x         60       x
Car 2      70x         70       x

The equation comes from the fact that Car 2 will have 
to travel 40 miles more than Car 1 in order to catch up.

           =  + 40 miles

              70x = 60x + 40
              10x = 40
                x = 4 hours

Edwin