Imagine a subject having 10% risk to die during the next 5 years as a result of complications of high blood pressure.
If his or her risk will decrease from 10% to 7% after after taking a hypertensive pill during several years, then
The absolute risk reduction will be 3% (10% - 7% = 3%),
The relative risk reduction will be 30% ((10% - 7%)/10% = 30%)