Replace every letter with a different digit between 0 and 9, such that you get a correct calculation.
The answer is 9567 + 1085 = 10652.
You can first see that M = 1. Then S = 8 or 9 and O = 0. MORE is at most 1098, and if S = 8, then E = 9, N is either 9 or 0, but this is impossible. Therefore S = 9, N = E + 1. You can check easily the 6 possibilities for (N, E) and then find the answer.
Henry Ernest Dudeney (1857 – 1930) was an English author and mathematician who specialized in logic puzzles and mathematical games. He is known as one of the country's foremost creators of mathematical puzzles.