$\quad C(4, 2) = \dfrac{4 \times 3}{2 \times 1} = 6$
\t
\\
$\quad C(10, 3) = \dfrac{10 \times 9 \times 8}{3 \times 2 \times 1} = 120$
\t
\\
$\quad C(12, 1) = \dfrac{12}{1} = 12$
\t
\\
$\quad C(5, 5) = \dfrac{5 \times 4 \times 3 \times 2 \times 1}{5 \times 4 \times 3 \times 2 \times 1} = 1!$
\t
\\
$\quad C(7, 5) = \dfrac{7 \times 6 \times {} \color{red}{5 \times 4 \times 3}}{\color{red}{5 \times 4 \times 3} \times 2 \times 1} = \dfrac{7 \times 6}{2 \times 1}$
$\qquad = C(7,2) = 21 \qquad$
\t
\\
$\quad C(10, 7) = C(10,3) = \dfrac{10 \times 9 \times 8}{3 \times 2 \times 1} = 120$
\t
\\
$\quad C(10, 0) = C(10,10) = 1$
\t