Ответ:

[tex]( \frac{1}{a + 5} - \frac{1}{a - 5} ) \div \frac{5}{a + 5} = \frac{a - 5 - a - 5}{(a + 5)(a - 5)} \times \frac{a + 5}{5} = \\ = - \frac{10}{5(a - 5)} = - \frac{2}{a - 5} = - \frac{2}{0.2 - 5} = \\ = - \frac{2}{ - 4.8} = 0.4[/tex]