[tex] \frac{6}{18} - \frac{7}{18} \times \left ( - \frac{2}{7} \right ) = \frac{6}{18} + \frac{7 \times 2}{18 \times 7} = \frac{6}{18} + \frac{2}{18} = \frac{8}{18} = \frac{4}{9} \\ [/tex]
