The weights of 4 boxes are 70, 50, 30 and 90 kilograms. Which of the following cannot be the total weight,in kilograms, of any combination of these boxes and in a combination a box can be used only once?
In a certain code language, 'x' represents '+', '÷' represents 'x', '-' represents '÷' and '+' represents '-'. Find out the answer to the following question.