Question 569942
They leave at the same time

Faster plane speed =500 mph

Faster plane after 1/2 hour has traveled 25 miles more.

so in 1 hourit will travel 50 miles more.

This means the slower plane speed = 450 mph
slower plane time = 1800/450= 4 hours

Faster plane time = 1800/500=3.6 hours= 

Now you can answer the question