Oh, you usually don't figure it out (though I heard that some autists could do it, but we're talking about the definition from way back, i.e. people at the top of the autistic spectrum). Instead, you learn by heart a bunch of formulas. Tbh, in order to be able to learn by heart long, meaningless formulas, you probably need to be a little on the spectrum as well. I can't imagine neurotypical people thinking: "Hey, what if I spent my weekend learning Rubik's Cube formulas?"