Question

An airplane went 960 miles
in the same length of time that a second plane went 1,200 miles. The speed of
the second plane was 40 miles an hour faster than that of the first. How long
did each plane travel?

Answer 1

Let   Air Plane A travel 960 miles   in  time   T hours 
         Speed of A = 960 / T  mph

Air Plane B traveled 1,200 miles    in  time  T hours
        Speed of B = 1200 / T  mph
 
Speed of B is 40 mph  more than speed of A

           1200 / T = 960 / T + 40 ,              Multiply by T
      
          1200 = 960  +  40 T
    
           40 T = 1200 - 960  = 240 
 
              T = 240 / 40 = 6 hours

Each plane traveled for 6 hours.