So first we divide (n÷2) so it will be s/(n÷2) =a+L. Next we subtract L and get s/(n÷2)-a. That's not it yet, since 2 is being divided in the denominator, we have to reciprocal it meaning multiply, it to the top value. So it would 2s/n-a=L. But you can just leave it like that if you desire and your teacher doesn't mind.
