计算：
(1)$-2.5÷ \frac {5}{8}× (-\frac {1}{4})$； (2)$25÷ (-5)× \frac {1}{5}÷ (-\frac {3}{4})$；
(3)$12× (-\frac {4}{3})÷ 5$； (4)$-2\frac {1}{5}× 2\frac {3}{11}÷ (-2\frac {1}{2})$；
(5)$(-2.1)÷ \frac {7}{10}× (-\frac {10}{7})$； (6)$-8÷ (-4)× \frac {4}{15}$；
(7)$(-3)× 6÷ (-2)× \frac {1}{2}$； (8)$(-\frac {4}{7})÷ (-\frac {3}{14})× (-\frac {7}{3})$；
(9)$(-3)÷ (+1\frac {3}{4})× 0.75× |-2\frac {1}{3}|÷ 9$； (10)$(-\frac {1}{42})÷ (\frac {1}{6}-\frac {3}{14}+\frac {2}{3}-\frac {2}{7})$.
(1)$-2.5÷ \frac {5}{8}× (-\frac {1}{4})$； (2)$25÷ (-5)× \frac {1}{5}÷ (-\frac {3}{4})$；
(3)$12× (-\frac {4}{3})÷ 5$； (4)$-2\frac {1}{5}× 2\frac {3}{11}÷ (-2\frac {1}{2})$；
(5)$(-2.1)÷ \frac {7}{10}× (-\frac {10}{7})$； (6)$-8÷ (-4)× \frac {4}{15}$；
(7)$(-3)× 6÷ (-2)× \frac {1}{2}$； (8)$(-\frac {4}{7})÷ (-\frac {3}{14})× (-\frac {7}{3})$；
(9)$(-3)÷ (+1\frac {3}{4})× 0.75× |-2\frac {1}{3}|÷ 9$； (10)$(-\frac {1}{42})÷ (\frac {1}{6}-\frac {3}{14}+\frac {2}{3}-\frac {2}{7})$.
答案：(1)1 (2)$\frac{4}{3}$ (3)$-\frac{16}{5}$ (4)2 (5)$\frac{30}{7}$ (6)$\frac{8}{15}$ (7)$-\frac{9}{2}$ (8)$-\frac{56}{9}$ (9)$-\frac{1}{3}$ (10)$-\frac{1}{14}$
解析：
(1)解：原式$=-2.5×\frac{8}{5}×(-\frac{1}{4})$
$=(-4)×(-\frac{1}{4})$
$=1$
(2)解：原式$=25×(-\frac{1}{5})×\frac{1}{5}×(-\frac{4}{3})$
$=(-1)×(-\frac{4}{3})$
$=\frac{4}{3}$
(3)解：原式$=12×(-\frac{4}{3})×\frac{1}{5}$
$=(-16)×\frac{1}{5}$
$=-\frac{16}{5}$
(4)解：原式$=(-\frac{11}{5})×\frac{25}{11}×(-\frac{2}{5})$
$=(-5)×(-\frac{2}{5})$
$=2$
(5)解：原式$=(-2.1)×\frac{10}{7}×(-\frac{10}{7})$
$=(-3)×(-\frac{10}{7})$
$=\frac{30}{7}$
(6)解：原式$=-8×(-\frac{1}{4})×\frac{4}{15}$
$=2×\frac{4}{15}$
$=\frac{8}{15}$
(7)解：原式$=(-18)×(-\frac{1}{2})×\frac{1}{2}$
$=9×\frac{1}{2}$
$=\frac{9}{2}$
(8)解：原式$=(-\frac{4}{7})×(-\frac{14}{3})×(-\frac{7}{3})$
$=\frac{8}{3}×(-\frac{7}{3})$
$=-\frac{56}{9}$
(9)解：原式$=(-3)÷\frac{7}{4}×\frac{3}{4}×\frac{7}{3}÷9$
$=(-3)×\frac{4}{7}×\frac{3}{4}×\frac{7}{3}×\frac{1}{9}$
$=(-3)×\frac{1}{9}$
$=-\frac{1}{3}$
(10)解：原式$=(-\frac{1}{42})÷(\frac{7}{42}-\frac{9}{42}+\frac{28}{42}-\frac{12}{42})$
$=(-\frac{1}{42})÷\frac{14}{42}$
$=(-\frac{1}{42})×\frac{42}{14}$
$=-\frac{1}{14}$
$=(-4)×(-\frac{1}{4})$
$=1$
(2)解：原式$=25×(-\frac{1}{5})×\frac{1}{5}×(-\frac{4}{3})$
$=(-1)×(-\frac{4}{3})$
$=\frac{4}{3}$
(3)解：原式$=12×(-\frac{4}{3})×\frac{1}{5}$
$=(-16)×\frac{1}{5}$
$=-\frac{16}{5}$
(4)解：原式$=(-\frac{11}{5})×\frac{25}{11}×(-\frac{2}{5})$
$=(-5)×(-\frac{2}{5})$
$=2$
(5)解：原式$=(-2.1)×\frac{10}{7}×(-\frac{10}{7})$
$=(-3)×(-\frac{10}{7})$
$=\frac{30}{7}$
(6)解：原式$=-8×(-\frac{1}{4})×\frac{4}{15}$
$=2×\frac{4}{15}$
$=\frac{8}{15}$
(7)解：原式$=(-18)×(-\frac{1}{2})×\frac{1}{2}$
$=9×\frac{1}{2}$
$=\frac{9}{2}$
(8)解：原式$=(-\frac{4}{7})×(-\frac{14}{3})×(-\frac{7}{3})$
$=\frac{8}{3}×(-\frac{7}{3})$
$=-\frac{56}{9}$
(9)解：原式$=(-3)÷\frac{7}{4}×\frac{3}{4}×\frac{7}{3}÷9$
$=(-3)×\frac{4}{7}×\frac{3}{4}×\frac{7}{3}×\frac{1}{9}$
$=(-3)×\frac{1}{9}$
$=-\frac{1}{3}$
(10)解：原式$=(-\frac{1}{42})÷(\frac{7}{42}-\frac{9}{42}+\frac{28}{42}-\frac{12}{42})$
$=(-\frac{1}{42})÷\frac{14}{42}$
$=(-\frac{1}{42})×\frac{42}{14}$
$=-\frac{1}{14}$