Need help with a drag down

Hi, I have a problem with a drag down as shown in the picture. (I removed "=" to make it easy for everyone to see my problem)

excel question.JPG

As you can see, I have a pattern to drag down the data and the only things changed are the red text.
However, when i tried to drag down, it did not work as it's supposed to be. (I did not drag down and get the 2nd set of data, I wrote it to explain the pattern)
I googled the solution but I could not find it.

Could you help me solve this problem
Thank you in advance.