The number of bottles in a full box is 12.
<u><em>Explanation</em></u>
Suppose, the number of bottles in a full box is
So, the number of bottles in <u>three</u> full boxes
Now, two more boxes are added, both of which have <u>one fewer bottle than the other three</u>. So, the number of bottles in these two boxes
As there were 9 bottles initially and now there are 67 bottles in the fridge, <em><u>so the equation will be</u></em>....
Thus, the number of bottles in a full box is 12.
