Your diagram is incorrect . . .
A plane is heading S 70° W with a groundspeed of 625 km/h.
If the pilot is steering west at an airspeed of 665 km/h,
. . what must be the windspeed and wind direction?
A o - - - - - - - - - - - o O
\ 20° *
\ * 625
The plane is flying from O to A at 665 km/hr.
The wind is blowing from A to B.
The plane's resultant flight is: . km/hr.
Law of Cosines: .
. . Hence: .
. . Hnce: .
Therefore, the windspeed is 227.4 km/hr and its direction is: .S 20° E.
Triangle ABO is virtually a right triangle . . .