B1:
a, $\frac{-17}{30}$- $\frac{11}{-15}$+ $\frac{-7}{12}$
= $\frac{-17}{30}$+ $\frac{11}{15}$- $\frac{7}{12}$
= $\frac{-5}{12}$
b, $\frac{-5}{9}$+ $\frac{5}{9}$:( $\frac{5}{3}$- $\frac{25}{12}$)
= $\frac{-5}{9}$+ $\frac{5}{9}$: $\frac{-5}{12}$
= $\frac{-5}{9}$+ $\frac{-4}{3}$
= $\frac{-17}{9}$
c, $\frac{-7}{25}$.($\frac{11}{13}$+ $\frac{2}{13}$)- $\frac{18}{25}$
= $\frac{-7}{25}$.1-$\frac{18}{25}$
= -1
B2:
a, x= $\frac{-21}{20}$- $\frac{-7}{15}$ =$\frac{-7}{12}$
b, ($\frac{7}{2}$-x). $\frac{5}{4}$ =$\frac{-21}{20}$
$\frac{7}{2}$-x = $\frac{-21}{25}$
x= $\frac{217}{50}$
