if an aircraft flying at 250km/h at bearing N 45East for 1 hour meets a wind from the NW at 50km/h, then how long will it take to fly the full 550km maintaining its N45E bearing to the ground with this wind blowing?

flying at 250 kph with a 50 kph cross wind

250 is the hypotenuse

the third leg (speed along heading) is
... √(250^2 - 50^2)

the angle (Θ) between the ground bearing and the flight bearing
... sin(Θ) = 50 / 250 ... towards N