Refer to figure.
Finding ground speed vector (drift angle, ground speed):

(1) Place the centre of disk on your TAS (500 kt).
(2) Place your true heading (180º) under the true index.
(3) Mark wind velocity (100 kt) downwards from centre.

NOTE:

When the question provides a track => mark wind velocity upwards from centre.
When the Heading is known => mark wind velocity downwards from centre.

(4) Place wind direction (225º) under the true index.
(5) Read ground speed and drift angle (note: Drift angle will be to the opposite side then marked on the flight computer) under the wind mark:

• Groundspeed: 435 kt