$\frac{5mn - m}{4m + n} * \frac{16m^2 - n^2}{5n - 1} = \frac{m(5n - 1)}{4m + n} * \frac{(4m - n)(4m + n)}{5n - 1} = \frac{m}{1} * \frac{4m - n}{1} = m(4m - n) = \frac{1}{4}(4 * \frac{1}{4} + 3) = \frac{1}{4}(1 + 3) = \frac{1}{4} * 4 = 1$

$\frac{(x + 2)^2}{3x + 9} * \frac{2x + 6}{x^2 - 4} = \frac{(x + 2)^2}{3(x + 3)} * \frac{2(x + 3)}{(x - 2)(x + 2)} = \frac{x + 2}{3} * \frac{2}{x - 2} = \frac{2(x + 2)}{3(x - 2)}$
 
$\frac{2(x + 2)}{3(x - 2)} = \frac{2(0,5 + 2)}{3(0,5 - 2)} = -\frac{2 * 2,5}{3 * 1,5} = -\frac{5}{4,5} = -\frac{10}{9} = -1\frac{1}{9}$
 
$\frac{2(x + 2)}{3(x - 2)} = \frac{2(-1,5 + 2)}{3(-1,5 - 2)} = -\frac{2 * 0,5}{3 * 3,5} = -\frac{1}{10,5} = -\frac{2}{21}$