Student or Learner
Are these sentences correct?
Mary's high blood pressure is well under control after three months off work. During the three months break she had the the time to exercise one hour daily and she believes this explained why her high blood pressure was under control.
The first one is fine. For the second, try:
During the three-month break, she had the time to exercise one hour daily, and she believes this explains why her blood pressure is under control.