the airplane has descended (25,000 - 19,000) = 6,000 feet
while flying (150 - 90) = 60 miles.
If the descent is modeled by a linear function, then the slope
of the function is
(-6000 ft) / (60 miles) = - 100 ft/mile .
Since it still has 19,000 ft left to descend, at the rate of 100 ft/mi,
it still needs to fly
(19,000 ft) / (100 ft/mile) = 190 miles
to reach the ground.
It's located 90 miles west of the runway now. So if it continues
on the same slope, it'll be 100 miles past the runway (east of it)
when it touches down.
