An enigma is a puzzle, or a situation that is perplexing, inexplicable, or ambiguous.

Synonyms can be puzzle, riddle, mystery, question, or conundrum.

A puzzle or an unknown circumstance. A situation that has not yet been solved with an explanation.
a mystery is like a puzzle and a secret

dilemma, conundrum, in a pickle, stickler

To solve something is to find a value or situation such that a given statement or situation is true.

A puzzle, a crossword, an equation, a crime etc may be solved.

Well, a conundrum is a situation, so just use common sense. If you can't you are the stupidest person alive.