You are able to combine any of the letters that are the same. For example, 5j + j = 6j. IF it has no variable (or letter) in front of it, you cannot combine it with anything that has a letter. For example, in your last problem, you can combine the 20 with the -14, the 8s with the 2s, but the c will remain by itself. You will have 6 + 9s + 2c for your answer. See if you can do the others by yourself.
