Ground speed can be determined by the vector sum of the aircraft's true airspeed and the current wind speed and direction
The plane is flying NW = 135°
The wind is blowing W25S = West and 25° South = 205°
The x vector component of the resultant is
500cos(135) + 120cos(205) = about -462.31
The y component of the resultant is
500sin135) + 120sin(205) = about 302.84
So the magnitude of the resultant vector [ the groundspeed ) = sqrt [ (-462.31)^2 + (302.84)^2] = about 552.67km/hr
And the angle of the resultant = tan-1(302.84/-462.31) = -33.23° + 180° = about 146.77° = about N56.77W
