b)$\frac{7}{-6}$ + $\frac{7}{12}$ + $\frac{5}{18}$ 

=$\frac{42}{-36}$ + $\frac{21}{36}$ + $\frac{10}{36}$ 

=$\frac{-42}{36}$ + $\frac{21}{36}$ + $\frac{10}{36}$ 

=$\frac{-11}{36}$

c)$\frac{-4}{7}$ + $\frac{2}{3}$ . $\frac{-9}{14}$

=$\frac{-24}{42}$ + $\frac{28}{42}$ . $\frac{-27}{42}$

=$\frac{-23}{42}$

d)8$\frac{2}{7}$ - (3$\frac{4}{9}$ + 4$\frac{2}{7}$

=$\frac{58}{7}$ - ($\frac{31}{9}$ + $\frac{30}{7}$)

=$\frac{522}{63}$ - ($\frac{217}{63}$ + $\frac{270}{63}$)

=$\frac{522}{63}$ - $\frac{489}{63}$

=$\frac{33}{63}$=$\frac{11}{21}$

Chúc bạn học tốt!