An airplane travels 2100 km at a speed of 500 km/hr encounters a head wind that decreases its speed to 400km/h for the next three hours and then travels the last 400km to complete the trip at an average speed for the entire trip of 440 km/h what was the speed of the plane for the last part of the trip

Need to work out the time and distance
it flew each segment.
2100/500=4.2 hrs
400 km for 3 hrs = 1200km
total distance = 2100 + 1200 + 400 = 3700km
av speed is 440km/h so total time travelled is 3700/440= 8.40909hrs so flew last distance in 8.4909-4.2-3=1.20909hrs
400km in 1.20909hrs
=330.827km/hr
which means I've read question wrong

I'm not sure exactly but my best guess would be 1/4