Answer:
The velocity of the cross-wind was 375 km/hr South
Step-by-step explanation:
The given speed of the airplane, v₀ = 500.0 km/hr W
The direction the airplane is headed = West
The direction of the wind encountered = Southbound wind
The final velocity of the airplane, R = 625 km/hr
The final direction of the airplane = South West SW
Let vₐ represent the velocity of the cross-wind
Therefore, we have the given velocities in vector form as follows;
R = -500.0·i - vₐ·j
Also, we have;

625² = (-500)² + (-vₐ)²
(-vₐ)² = 625² - (-500)² = 140625
-vₐ = 375
vₐ = -375 km/hr North = 375 km/hr South
The velocity of the cross-wind = vₐ = 375 km/hr South