TWO AIRPLANES LEAVE DALLAS AT THE SAME TIME AND FLY IN OPPOSITE DIRECTIONS. ONE AIRPLANE TRAVELS 80 MILES PER HOUR FASTER THAN THE OTHER. AFTER THREE HOURS, THEY ARE 2940 MILES APART. WHAT IS THE RATE OF EACH AIRPLANE?

The two planes start at the same place and are 2940 miles apart, 3 hours later. Thus the distance between them is increasing at a rate of  ²⁹⁴⁰/₃ = 980 ^miles/_hour. In other words, the sum of the speeds of the two planes is 980 ^miles/_hour.

Now can you finish the problem? Make sure that you check that your answer is correct.