The plane's velocity of 35.11 m/s is actually due in a north-eastward direction. The 12 m/s velocity is the vertical component of the plane's velocity, hence it is pointing northwards. We will use the formula:
Vy = Vsin∅
To determine the angle ∅ at which the plane is flying. This is:
12 = 35.11 * sin∅
∅ = 20.0 degrees
The eastward velocity is:
Vx = Vcos∅
Vx = 35.11 * cos(20)
Vx = 33.0 m/s
The plane's eastward velocity is 33.0 m/s