Question

Find the four arithmetic means between 12 and -13.

Answer 1

You're dividing the distance between 12 and -13 into 5 parts (remember, there's a part on each side of the mean, so we have one more part than we do means). What is 12-(-13)? What is that divided by 5? Once you know that, march along from -13 to 12, adding that quantity each time...