$f,\dfrac{-8}{9}-\dfrac{1}{9}.\dfrac{2}{9}-\dfrac{1}{9}.\dfrac{7}{9}$
$=\dfrac{-8}{9}-\dfrac{1}{9}.(\dfrac{2}{9}+\dfrac{7}{9})$
$=\dfrac{-8}{9}-\dfrac{1}{9}.\dfrac{9}{9}$
$=\dfrac{-8}{9}-\dfrac{1}{9}.1$
$=\dfrac{-8}{9}-\dfrac{1}{9}$
$=\dfrac{-9}{9}$
$=-1$