Question

$frac{n-1}{2n} - frac{n+1}{5n}$

Answer 1

$frac{5n-5-2n-2}{10n} = frac{7n+7}{10n}$

Answer 2

$frac{n-1}{2n}- frac{n+1}{5n}= frac{(n-1)5}{2n*5}- frac{(n+1)2}{5n*2}= frac{5n-5-2n-2}{10n}= frac{3n-7}{10n}$