Well, just like the similar question asked before, it is answered like this. We just take note that if the question asks about "midway" it is likely that it is asking for the average. To find the midway of 21 and 25, we add the terms and divide the resulting sum by the number of terms added. It is just like this:
What is the midway of 21 and 25?
(Take note that the denominator is 2 because the number of terms we added is 2 and they are 21 and 25.)
Therefore, the midway of 21 and 25 is 23.