A college bookstore ordered six boxes of red pens. The store sold 37 red pens last week and 67 red pens this week. 4 pens were left on the shelf. How many pens were in each box?

(37 + 67 + 4) / 6 = ______?

18

To find out how many pens were in each box, we need to subtract the number of pens sold from the total number of pens ordered and then divide the result by the number of boxes.

First, let's calculate the total number of red pens sold:

Total red pens sold = red pens sold last week + red pens sold this week
Total red pens sold = 37 + 67
Total red pens sold = 104

Next, let's find out how many red pens were left:

Red pens left = Total red pens ordered - Total red pens sold
Red pens left = 6 boxes * pens per box - 104
Red pens left = 6 * pens per box - 104

We know that 4 pens were left on the shelf, so we can set up the equation:

4 = 6 * pens per box - 104

Now, let's solve for the number of pens per box:

6 * pens per box = 4 + 104
6 * pens per box = 108

Dividing both sides by 6:

pens per box = 108 / 6
pens per box = 18

Therefore, there were 18 pens in each box.