Two passenger airplanes depart from an airport simultaneously. One flies east at 400mi/h, and the other flies west at 450mi/h. Determine how long it will take the planes to be 2,975 miles apart.

Let "t" be the time after planes to be 2,975 miles apart.

400t+450t=2975.

850t=2975.

t=2975/850

=3.5Hours.