Penelope eats 4 chocolates per day, because in one day, 20 chocolates are in the box. Then, after 2 more days, 8 chocolates are eaten. That means, if she eats an even amount of chocolates, she eats 4 chocolates per day. To check this pattern, on the fourth day, there are 8 chocolates left. 12 - 8 = 4, and the pattern would continue. On the fifth day, 4 chocolates would be left, and on the sixth day, 0 chocolates would be left.
