How to access the "Transform" function?

The problem is this: I want to limit the rotation of the camera vertically, I decided to do it using “if”, referring to the “Transform” of the camera, so that if, for example, the degree by “Rotation X> 90” then “Rotation X = 90”. But I don’t know how to write it correctly. Maybe there is an easier way to limit the rotation of the camera, then it will also pass for an answer. Thanks to everyone who helps!

You can clamp any value using mathf.clamp