I have found this puzzle on the internet but I didn't get any answer yet, so help me out.
For rules see the given image:
Here you can either give clues or may explain your answer.
The answer is
the right-hand side is the last letter of the sum of all digits on the left-hand side. Thus 1111 -> FOUR, 2222 -> EIGHT, 3333 -> TWELVE, 4444 -> SIXTEEN, 5555 -> TWENTY.