I think the subtraction is associative operation since Where, 6 - 2 - 3 isn't equal to 6 - (2-3) as you mentioned but it equals to 6 - (2 + 3), because if we use 6 - (2-3) that means we will multiply 6 + (2 * - 1) + (-3 * -1) ; and the original sign of 3 is (-) and should be remained the same after putting the parentheses so, it would be 6 - ( 2 + 3) to remain the original signs.
+김성주 2^3 is read "2 to the *power of 3*" and the operation is named exponentiation. It has two intended meanings: that exponentiation is powerful and a pun with "power of exponentiation".
+김성주 Puns are generally something that have to be apologized for after they are made, so he was being sarcastic when he said the joke was hilarious. If he had made that joke in an actual live classroom, then he most likely would have heard groans and might possibly have been hissed.
10:42, Sir apologies, but I would like to point out your mistake there, When you used precedence, you should have used positive sign inside the parenthesis instead of negative because minus sign was taken as a common, that would result in positive sign inside, so this operation is also associative, thats what I say. Point me out if I am wrong. Thank you.