Operator precedence, multiplication and division take precedence over addition and subtraction It reads :- 50 + 50 - (25*0) + 2 + 2 = 104 Operator precedence in maths and computing : exponentiation and roots multiplication and division addition and subtraction I use RPN personally which reads as 50 Enter 50 + 25 Enter 0 * - 2 + 2 + or 50 Enter 50 plus | stack result 100 25 Enter 0 times | stack result 0 minus | stack result 100 2 plus | stack result 102 2 plus | stack result 104 RPN stands for Reverse Polish Notation and is the way that old fashioned adding machines used to work, the ones with the handles. It is also the way you were taught to do arithmetic as a kid you would write down a list of numbers and then do the operation for example 5 + 4 9
The brackets are implied by the rules of operator precedence, operators are the * / + - symbols on a computer, multiply, divide, add, subtract, and in the teaser you still have to apply operator precedence rules which is why the 25*0 or (25x0) disappears (results in zero) as operator precedence says it has to be evaluated first.
My daughter Janna posed one of these on Facebook, it was a little harder as it was a symbolic algebra problem using pictures but I got it wrong at my first try although I was convinced I had got it right, I misinterpreted the value associated with one of the symbols (a banana) and it's use in the formula and had to apologise to my daughter and tell her she was right and dad was wrong, even though dad is supposed to be clever