#### Answer

$\frac{1}{25}$

#### Work Step by Step

$(\frac{1}{10}-\frac{3}{20})(\frac{1}{5}-1)$
$=(\frac{2}{20}-\frac{3}{20})(\frac{1}{5}-\frac{5}{5})$
$=(-\frac{1}{20})(-\frac{4}{5})$
$=--(\frac{1}{20}\times\frac{4}{5})$
$=\frac{1}{20}\times\frac{4}{5}$
$=\frac{1}{5}\times\frac{1}{5}$
$=\frac{1}{25}$