Took blood pressure in my left arm 117/77 but when i took my blood pressure on my right arm it was 124/87. why the difference?

Because we are not: perfectly symmetrical, and because each moment is unique and not perfectly reproducible there can be small variations in blood pressure. 10 mm or less, such as noted in your measurements, are considered normal. If there is larger difference, one has to consider whether there might be some arterial plaque/obstruction in the higher pressure arm. This might be a marker for vascular disease elsewhere.

Varying bp: Hi Derrick, to explain it simply, you have a different configuration of arteries from the right arm to the left. Some vessels are slightly larger than others. This effects pressure. A difference of 7mmhg is not clinically significant and should not be anything to worry about. Concern would start at a difference of 20mmhg. Hope thats helpful.

Normal variation: Blood-pressure's can vary by 5 to 10 mmHg on either side due to positioning blood vessels musculature etc. that is not a very significant difference if there is a really large difference like over 20 mmHg than that something possibly needs to be evaluated.