Since you are told that the chocolates can be shared with 4 or 5 friends and will have two extra left, then we can say that the possible number of chocolates is a factor of 4 and 5 plus two being the extra.
---------
In this case, we will find the least common multiple of 4 and 5 to get a number.
4 - 4, 8, 12, 16, 20, 24, 28, 32, 36, 40
5 - 5, 10, 15, 20, 25, 30, 35, 40, 45, 50
the least common multiple as we can see is 20.
since there will be two chocolates left then we say that the possible number of chocolates is 20 + 2 = 22
