Out of 3 blood pressure measurements, which one should I choose?

The average of the three readings, which is 120 66 70

@evillarreal Welcome to Mayo Connect. And thank you for asking something that many people would like to know, but wonder about.
Armando is correct, when 3 blood pressures are taken within a few minutes and under the same conditions, the practice is to average them. You can also select the middle one to represent the average.

When blood pressure is taken on different days, or under different conditions (for example, sitting and standing) each one is recorded. Our blood pressure can fluctuate from day to day and hour to hour depending on when it is taken, what we have had to eat or drink, whether we have been exercising or are under stress, whether we are ill, medications taken...

What you should watch is whether your usual blood pressure is within the accepted range for you age and gender.
Here is the current accepted chart of normal and elevated blood pressures:
Women Men
18-39 years 110/68 mm Hg 119/70 mm Hg
40-59 years 122/74 mm Hg 124/77 mm Hg
60+ years 139/68 mm Hg 133/69 mm Hg

Beyond the averages in the blood pressure chart by age and gender above, adult blood pressure falls into one of five categories:
Category Systolic Diastolic
Normal Less than 120 and Less than 80
Elevated 120–129 and Less than 80

And the pressures considered High
High Blood Pressure (Hypertension) Stage 1 130–139 or 80 – 89
High Blood Pressure (Hypertension) Stage 2 140 or higher or 90 or higher
Hypertensive Crisis – Consult your doctor immediately Higher than 180 and/or Higher than 120
https://www.baptisthealth.com/blog/heart-care/healthy-blood-pressure-by-age-and-gender-chart
Do you have concerns about your blood prerssure?
Sue

Thank you both for your immediate response. I forgot to mention several factors and that is that I am 75, and have lost 40 pounds in 12 weeks and had not eaten for more than 12 hours and that I had completely rested for 10 minutes before I started the tests. I performed the tests one right after the other without waiting. Last Friday I had to go to the VA emergency and had to walk on crutches for almost a 1/4 of a mile just to get to the ER room. When they took my blood pressure it was 150. So I do understand how the blood pressure will fluctuate with extreme stress like exercise. So it appears that according to your chart, 60+ years 139/68 mm Hg 133/69 mm Hg, I should not be too worried if my readings stay below the 130's. Again, thank you so much for your help in these times when I don't have a primary care physician to help me. I am in the process of getting a PCP in November. I am waiting on the VA to schedule a physical.

So, as you have now experienced, sphygmomonometers are neither perfect nor exact. The variance in readings is well within tolerance.
And you are absolutely right that your readings are acceptable for your age.

Good luck getting a new PCP.
Sue