first, find a common denominator (6) and multiply all numbers by it. You will be left with 2x + x = 21. Then, combine like terms to get 3x = 21. Divide both sides by 3 to get x = 7.
You know this because if they show up to the store with the same amount of money and SPLIT the amount of money for the cookies, they will still have the exact same amount.
