Each week a different problem or challenge will be posted here. Solve the problem in the comments section of the post. Put the challenge number at the start of your answer and don't forget to explain/show how you got your answer!
6 + 4 = 10 and 6 - 4 = 2 so the answer to the first problem is 210
15 + 3 = 18 and 15 - 3 = 12 so the answer to the last problem is 1218