*It is a double-bracket because there is a bracketed equation inside a bracketed equation, so as to separate the values from the unit, in this case, the $ sign. Take 18-6 to find the total cost of the notepads, and take that value divided by 3, the price of one notepad, to find the number of notepads bought.
The answer is (18-6)/3. You have to take the six dollars of the magazine from the total, then divide the remaining money by the price of the notepads to find the amount of notepads bought. I Hope This Helps!!!
