How Do You Manage Duplicate

So here's my question. Suppose a user on my Support Forum can immediately get an answer to a topic they are about to create and all they have to do is search the forum. I don't want to merge their post with a topic that already exists if the topic already answers their question.

Maybe they do the search but the search doesn't find the topic. So, over time you wind up with 5, 10 or more topics that ask "How do I do XYZ" and my reply simply points them to another topic that already answers their question. Is the answer to just Delete their topic and send them a PM to a link to the topic and advise them to read the topic and post questions there? Otherwise, we wind up with the same question being asked in different topics.

What is your solution to manage this?

Reference https://www.phpbb.com/community/viewtopic.php?f=556&t=2426411

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