Davey and Charlie shared half a box of crackers.  They each had  20 crackers.  How many crackers did the box have when it was full?

20×2=40×2=80

In the problem  it said that there were two boys they each had 20 crackers witch is half the box.  I took 20 multiplied it by 2 for both  the boys and got 40.  Then I multiplied that by 2 because they ate half the box.  I got 80.  So that is my answer   that is how many crackers were in the box when it was full.