Three Investigators

Series of "teen mysteries". Key protagonist was Jupiter Jones. https://www.threeinvestigatorsbooks.com/ https://en.wikipedia.org/wiki/Three_Investigators

Series order: https://en.wikipedia.org/wiki/The_American_series_of_The_Three_Investigators

https://thrillingdetective.com/2021/02/13/jupiter-jones-bob-andrews-pete-crenshaw-the-three-investigators/

Sold under the Alfred Hitchcock label, but he had nothing to do with it, didn't even write the introductions that were listed as being by him.

I discovered this series rather late, so only read a few of them.

A challenge to get in print https://www.amazon.com/gp/bookseries/B00CKDKJGU/