Scripting error in

I am following a tutorial called Roll A Ball and I am following the script exactly but, I am still getting an error message and I am not understanding why.

other.gameObject.SetActive(false) ; This is the code I am receiving the error with. It is telling me that the name other.gameObject.SetActive(false) ; and the name SetActive does not exist in the current context.
Not sure what to do next your help would be greatly appreciated

You should send the complete script before anyone can figure out what is wrong.
Use the code sample button in the forum editor to paste your code