A plane travels due north with a velocity of 50 m/s and the qind blows due north east 30 degrees at a velocity of 20 m/s find the magnitude and direction of the planes velocity relative to the ground

Its nothing but the resultant of those two velocity vectors which are separated by 30 degrees.

resultant^2 = 50^2 + 30^2 + 2(30)(50)cos30