Answer:
Let's suppose that the ideal blood pressure is 100 (the ideal values are between 90 and 110, i am taking the middle value)
If 125 is the 100%, and we want to go to 100, then we need to decrease by:
125 - 100 = 25
now, to calculate the percentage that represents the 25, we need to calculate:
(25/125)*100% = 20%
So to reduce his blood pressure to normal, he must reduce it by 20%