I want to use truth tables to show that equations can be satisfied or not, or if they are valid. not(X→(Y→X)) (X∧(notX→notY))→Y I would say the first one is valid, because of the not in front of it, it's always true. I don't know about the second one. I don't know how to split them up best to use a truth table. I guess I can/should use: X, notX, notY, Y, X∧(notX→notY), notX→notY and (X∧(notX→notY))→Y.