Question 164423
Rate x Time = Distance
Rate with wind = Speed of Plane in calm air + Speed of Wind={{{R[w]=P+W}}}
Rate against wind = Speed of Plane in calm air - Speed of Wind={{{R[a]=P-W}}}
Distance is the same in both cases. 
Time with : {{{T[w]=4}}}
Time against : {{{T[a]=5}}}
Distance : {{{D=800}}}
Generate your two rate equations in terms of P and W and the known quantitites.
Solve for P and W.