let the plane is flying at some angle theta with west towards north
Now we can use the components
[tex]v_y = 320 sin\theta[/tex]
[tex]v_x = 320 cos\theta[/tex]
now since plane has to fly towards west so net speed in north must be equal to speed in south for air
So we can say
[tex]320 sin\theta = 80[/tex]
[tex]sin\theta = \frac{1}{4}[/tex]
[tex]\theta = 14.5 degree[/tex]
so plane has to fly in direction 14.5 degree North of west