Converting mmHg to atm is solved by division.
Example: Convert 745.0 to atm.
Solution- divide the mmHg value by the 760.0 mmHg / atm.
745 mmHg over 760.0 mmHg/atm
atm value is 0.980263
Now, I am a medical student and we have never had to convert a BP (blood pressure) to atm from mmHg, only ever kPA. SO, I am going to take a guess here and say that when you do the work to solve this, you are going to convert the Systolic (upper #) which is the 145. You should get 0.190789 and then convert the Diastolic (lower #) which is 65. You should get 0.08552632.
So your fraction so to speak should read, 0.190789/0.08552632 or 0.190789 over 0.08552632
(Just to note that is way to low of a BP, although it is irrelevant) Best wishes and good luck. "Remember, never just look for the right answer, look for why it is the right answer!"