[tex] \frac{1}{2} - \frac{5}{19} \times ( \frac{5}{2} - \frac{3}{2} \times \frac{2}{5}) = \\ \\ \frac{1}{2} - \frac{5}{19} \times ( \frac{5}{2} - 3 \times \frac{1}{5}) = \\ \\ \frac{1}{2} - \frac{5}{19} \times ( \frac{5}{2} - \frac{3}{5}) = \\ \\ \frac{1}{2} - \frac{5}{19} \times \frac{19}{10} = \\ \\ \frac{1}{2} - 5 \times \frac{1}{10} = \\ \\ \frac{1}{2} - \frac{1}{2} = \\ \\ 0 [/tex]
