12. 能简便的用简便方法计算。
$5\sqrt{13} × 4 × 2\sqrt{13}$ $(2\sqrt{13} = 2 × \sqrt{13})$ $2\sqrt{2} - \sqrt{2} + 10\sqrt{2}$
$(-\frac{1}{2}) × (-\frac{2}{3}) × (-\frac{3}{4}) × (-\frac{4}{5})$ $-3^2 × (-3)^2$

$520$ $11\sqrt {2}$ $\frac {1}{5}$ $ -81$