Combine like terms: group the \(c\) terms and the constant separately.<br><br>
&bull; Like terms with \(c\): \(3c + 6c = 9c\)<br>
&bull; Constant: 7 stays as is.<br>
&bull; Result: \(9c + 7\)<br><br>
Final Answer: C: \(9c + 7\)