(F + 40) * 5/9 - 40 = C (C + 40) * 9/5 - 40 = F Takes advantage of the fact that -40 F and -40 C are the same. Remember it as (move origin -- convert -- move

(F + 40) * 5/9 - 40 = C (C + 40) * 9/5 - 40 = F Takes advantage of the fact that -40 F and -40 C are the same. Remember it as (move origin -- convert -- move origin back). I find it easier as a I don't have to remember precedence rules and the multiplication is obvious.