Mary is x years old. She is 6 years older than her twin brothers Sam and Paul. What is the mean age of the three children?

\(mean= \frac{\mathrm{sum\text{ }of\text{ }several\text{ }given\text{ }values} }{\mathrm{number\text{ }of\text{ }values\text{ }given}} \)
\( \frac{\mathrm{[x+(x-6)+(x-6)} }{\mathrm{3}}\)
\(\frac{\mathrm{(3x-12)} }{\mathrm{3}}\)
\(\frac{\mathrm{3(x-4)} }{\mathrm{3}} = x-4\)