$$ \dfrac{-11}{18} + \dfrac{-3}{9} + \dfrac{2}{-3} $$
It can be written as
$$ \dfrac{-11}{18} + \dfrac{-3}{9} + \dfrac{-2}{3} $$
LCM of $$3 , 9 $$ and $$18 $$ is $$18 $$
$$ = \dfrac{-11 \times 1}{18 \times 1} + \dfrac{-3 \times 2}{9 \times 2} + \dfrac{-2 \times 6}{3 \times 6} $$
By further calculation
$$ = \dfrac{-11}{18} + \dfrac{-6}{18} + \dfrac{-12}{18} $$
So we get
$$ = \dfrac{-11 - 6 - 12}{18} $$
$$ = \dfrac{-29}{18} $$