The basic way to explain this, is that you have to remember that they have to be exclusive. Exclusive meaning that they cant be all the same, if they the same for example in a 2 input XOR: 0 0 ==> 0 (They arent exclusive) 0 1 ==> 1 (They are exclusive) 1 1 ==> 0 (They are not exclusive) and so on and so forth. Now you have to just expand this to a 3 input XOR ex: 0 0 0 ==> 0 (Take a look at the first 2, they are not exclusive so that will give you a 0, Now take that and you have 0 0 which is also NOT exlcusive. Your final answer is 0) 0 0 1 ==> 1(The first 2, they are not exclusive so you will get a 0. Now take that and you have 0 1, this is exclusive. Your final answer is 1) 1 1 1 ==> 0 (The first 2 are not exclusive so you get a 0. Now take that and you have 0 1, this is exclusive. Your answe will be 1) This is the same for the rest of the truth table.