Câu 1.7. Tính
a. $-\frac{6}{18}$ + $\frac{18}{27}$= $-\frac{1}{3}$ + $\frac{2}{3}$=$\frac{1}{3}$
b. 2,5-($-\frac{6}{9}$) = $\frac{25}{10}$+ $\frac{6}{9}$= $\frac{5}{2}$+$\frac{2}{3}$= $\frac{15+4}{6}$=$\frac{19}{6}$
c. -0,32.(-0,875)= -$\frac{32}{100}$.(-$\frac{875}{1000}$)= -$\frac{8}{25}$. (-$\frac{7}{8}$)= $\frac{7}{25}$
d. (-5): 2$\frac{1}{5} $= (-5): $\frac{11}{5} $=-$\frac{25}{11} $