You can't.

But you can remove a page from a category by deleting the text [[Category:Car Mastery]] at its bottom.

Only when one of the above-mentioned categories is completely empty, an admin will delete it as a whole.

As long as there are pages which still have the [[Category:Car Mastery]] at their bottom, the category will be "recreated".

Ah, and if you can't see the code at the bottom of the page: Please switch to Source Editor (dropdown menu of the Edit button). You should always edit with source editor by the way. The Visual Editor is buggy and destroys page layouts from time to time, and the other editors are not much better. Source code may be a bit less intuitive at the beginning, but it's the real thing if you want to do advanced editing.

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