Question 840771
speed = distance / time taken

speed along with the wind a = 390/ 2 => 195 miles/hour

speep against the wind b = 330/2 => 165 miles/ hour

Speed of still air = (speed along the wind + speed against the wind)/2

speed of the wind = (speed along the wind - speed against the wind)/2

speed of still air = (195+165)/2 => 360/2 => 180

speed of the wind = (195-165)/2 => 30/2 => 15