The way I did this is if she bought 3 times as many bags of chips the pretzels, I say take 1 bag of pretzels and then add 3 bags of chips. Then I multiply 4x7 and get 28. So there's 21 bags of chips, and if there's 7 bags of pretzels and 3 times as many chips. And we know that 21 is 3 times as much as 7. So there's 7 bags of pretzels and 21 bags of chips.
