I'm assuming you want to simplify \(c+2c+3c\).
c, 2c, and 3c are called like terms. Like terms have variables that are the same and exponents that are the same. Is that the case here? It certainly is. c, 2c, and 3c all have the same variable of c. Also, these terms all have the same exponent: 1. It may not be visibly obvious, but anything raised to the power of 1 is itself. To simplify, add the coefficients: