What is the distance between #(-4,-2,12)# and #(-4,3,-12)#?
The Pythagorean Theorem gives the squared distance as the sum of squares of the difference of each coordinate:
There's not really another way to check it other than to do it again. Oh yeah, we could have someone else do it. My go-to expert is Wolfram Alpha. Alpha's even kind enough to work out the approximation and draw a picture. It really is an amazing gift to the world.