Vote for the SOLUTION as helpful

We use discourse-solved plugin in our forum and works fine but we need to add extra functions that way we can observe how much the provided solutions are working with people.
we need to measure how effective these solutions are but adding some button the users who read the solution can vote as helpful or not.
if the votes as unhelpful go above the helpful votes we may remove the solution from the topic to ensure the quality of the answers.

Please advise if we can achieve such a thing.

Those options don’t exist in Solved today, Discourse has no concept of downvotes to negatively score contributions.

Your obvious options are to either fork solved (and offer the additional functionality as a PR), or find someone via the #marketplace.