The margin of error of a result is the range in which an error can vary. To find the margin of error between both distances we have to
28-12 = 16, that is, the variation of the result has a range of 16 miles. So we will look for the midpoint of both distances
(X2-X1)/2+X1=(28-12)/2+12=16/2+12=8+12=20
So from this midpoint the value can vary between 8 points below and 8 points above that would cover the difference of 16 miles that we observed at the beginning
In this way, the correct answer is 20 miles with an error margin of ± 8 miles
