All you have to do is combine like terms. 2c and (-c) are like terms (-5b) and (-b) are like terms and a is a term. So, 2c combined with (-c) is C. (-5b) and (-b) combined is (-6b). Since a doesnt need to be combined with anything, you leave it as it is so your answer will then be c - 6b + a (this is the answer assuming that there is a + in front of the a. If there is a - sign, then just change your +a to -a at the end