So the midpoint of AB can be calculated by finding the length of AB, dividing it by 2 and then adding it to A. So the length of AB is equal to B-A or in general the difference between two values is |a-b| where the order doesn't matter, but assuming B is the right side (meaning it should be greater than A) the length should be B-A. in this case A = -5 and B = 3 so the length is 3 - (-5) = 8. The length is 8 so the midpoint is half of that which is 4, now adding 4 to the left side (A) you get -5 + 4 = -1. So the midpoint of AB lies at -1. Now the midpoint of AC can be found using the same process. 7 - (-5) = 12 => 12/2 = 6 => -5 + 6 = 1 so the midpoint of AC is at 1. Now to find how many units from the midpoint AB to AC you just subtract the midpoint of AB from AC. this gives you 1 - (-1) which is 2.
