\[\boxed{\mathbf{229.}}\]
\[\textbf{а)}\ C_{3}^{3} = 1.\]
\[\textbf{б)}\ C_{5}^{3} = \frac{5!}{3!2!} = \frac{4 \cdot 5}{2} = 10.\]
\[\textbf{в)}\ C_{7}^{3} = \frac{7!}{3!4!} = \frac{5 \cdot 6 \cdot 7}{2 \cdot 3} = 35.\]
\[\textbf{г)}\ C_{n}^{3}.\]