Application of variation 3

On a nautical chart, to convert a True Course to a Magnetic course, or to convert a True Bearing to a Magnetic bearing you must apply the following formula:
From True to Magnetic, add the Westerly Variation and subtract the Easterly Variation.
To convert a Magnetic Course to a True course, or a Magnetic Bearing to a True bearing you must apply the following formula:
From Magnetic to True, subtract the Westerly Variation and add the Easterly Variation.