\[\boxed{\text{760\ (760).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[\textbf{а)}\ A_{6}^{2} = \frac{6!}{4!} = 5 \cdot 6 = 30.\]
\[\textbf{б)}\ A_{6}^{4} = \frac{6!}{2!} = 3 \cdot 4 \cdot 5 \cdot 6 = 360.\]
\[\textbf{в)}\ P_{6} = 6! = 720.\]