Can some one help me? Please!
\(\frac{1}{3}(n+3)=6\\ n+3=18\\ n=15 \Rightarrow C\)
\(\frac{1}{3}(n+3)=6 \\ \frac{1}{3}n+1=6 \\ -1\ \ \ \ -1 \\ \frac{1}{3}n=5 \\ n=\boxed{15}\)