You know that the sum of a and b is 24, because the average is the sum of the numbers divided by the amount of numbers added together, and 12*2 is 24. Add 3 to 24 so you have 27, and then divide that by 3 because there are now 3 numbers in the set. The average of a, b, and c is 9.
Mowgli's battle/affair with shere khan
This isn't neccessarily true. Your introduction can still make sense without the hook, and the information inside the introduction part should really not directly depend on the hook to explain them, they should either be self explanatory, or you should explain them there.
Hopefully this helps!
