$$ \dfrac{4}{7} + 0 + \dfrac{-8}{9} + \dfrac{-13}{7} + \dfrac{17}{9}$$
$$ = \left [ \dfrac{4}{7} + \left ( \dfrac{--13}{7} \right ) \right ] + \left (\dfrac{-8}{9} + \dfrac{17}{9}\right ) $$
$$\left [ \dfrac{4}{7} - \dfrac{13}{7} \right ] + \left [ \dfrac{-8}{9} + \dfrac{17}{9} \right ]$$
$$ = \dfrac{-9}{7} + \dfrac{9}{9} = \dfrac{-9}{7} + 1 $$
$$ = \dfrac{-9 \times1}{7 \times1} + \dfrac{1 \times7}{1 \times7}(\therefore LCM of 1and 7 = 7 ) $$
$$\dfrac{-9}{7} + \dfrac{7}{7} = \dfrac{-2}{7} $$