$\frac{2}{51}-\frac{2}{5}(\frac{1}{2}-\frac{5}{51})$
$=\frac{2}{51}-\frac{2.1}{5.2}+\frac{2.5}{5.51}$
$=\frac{2}{51}-\frac{2}{10}+\frac{2}{51}$
$=\frac{4}{51}-\frac{1}{5}$
$=\frac{4.5}{51.5}-\frac{1.51}{5.51}$
$=\frac{20}{255}-\frac{51}{255}$
$=-\frac{31}{255}$