This is commonly called a reduction in complexity theory, and is used often in hardness proofs. Here is a class from an incredible teacher, Erik Demaine , about

This is commonly called a reduction in complexity theory, and is used often in hardness proofs. Here is a class from an incredible teacher, Erik Demaine , about such problems which may be helpful: MIT 6.890 https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-890-algorithmic-lower-bounds-fun-with-hardness-proofs-fall-2014/ https://ocw.mit.edu/courses/electrical-engineering-and-compu... Basic idea is map a hard problem A (e.g TSP) to some other problem X (e.g chess) by finding “gadgets” then you know X is at-least as hard as A (a lower bound on X).