(creg needed chips so he priced the box that had 4 packages of chips in it. The box sold for .84. Separately the chips sold for .25 a package. He bought the box of 4 packages plus the one package so he would have 5 days of lunches. How much more did he pay for the individual package by purchasing it separate from those in the box? )
So the question is asking you to compare the cost of a single bag of chips and the cost per bag when purchased in a box.
The first number is given to you: "Separately the chips sold for $0.25 a package."
The second number we have to work for. The box has 4 bags of chips in it and he paid $0.84 for the box. Since there were 4 bags, you need to work out what 1/4th of $0.84 is. i.e.
$0.84/4 = x
Now that you know how much each bag of chips cost when in the box (x), you compare that to the $0.25 per bag separately. They even tell you that the individual bag is more so
$0.25 - x = ??
And that's your answer. :)