Answer:
(any variable can be used in place of "pH")
Explanation:
Since the pH has to be between 7.2 and 7.8, it is more than 7.2 and less than 7.8.
The less than equal to sign was used because the pH can also equal 7.2 and 7.8.
Like mentioned, any variable like x can be used instead of the "pH" I put in the equation, but make sure to define your variable.
Hope I helped!!! :)