Упростите выражение 7 класс. Заранее благодарю

Решите задачу:

$( \frac{5c ^{2}-c }{25c ^{2}-10c+1 }+ \frac{4}{1-25c ^{2} } ):(1- \frac{3}{5c-1} )- \frac{c}{5c+1 } \\ ( \frac{c(5c -1) }{(5c -1) ^{2} }+ \frac{4}{(1-5c)(1+5c) } ):( \frac{5c-1-3}{5c-1} )- \frac{c}{5c+1 } \\ ( \frac{c }{(5c -1)}- \frac{4}{(5c-1)(5c+1) } ):( \frac{5c-4}{5c-1} )- \frac{c}{5c+1 } \\ (\frac{c(5c+1)-4}{(5c-1)(5c+1) } ):( \frac{5c-4}{5c-1} )- \frac{c}{5c+1 } \\ (\frac{5c^{2}+c-4}{(5c-1)(5c+1) } ):( \frac{5c-4}{5c-1} )- \frac{c}{5c+1 } \\$
$(\frac{(5c-4)(c+1)}{(5c-1)(5c+1) } )*( \frac{5c-1}{5c-4} )- \frac{c}{5c+1 } \\ \frac{c+1}{5c+1} - \frac{c}{5c+1 } = \frac{c+1-c}{5c+1} = \frac{1}{5c+1}$