Speed = Distance/Time
With the wind:
x + y = 2500/225
Against the wind:
x - y = 2500/270
225 = 3h 45m
270 = 4h 30m
x = Plane's speed
y = Wind's speed
225x + 225y = 2500 (1)
270x + 270y = 2500 (2)
Simultaneous equations, I'm sure you can solve it from here.