Câu 1:

a) $\frac{-2}{7}$ x $\frac{21}{8}$ 

= $\frac{-2 x 21}{7 x 8}$ 

= $\frac{-42}{56}$ 

= $\frac{-3}{4}$ 

b) $\frac{-5}{23}$ : (-2)

= $\frac{-5}{23}$ : $\frac{-2}{1}$ 

= $\frac{-5}{23}$ x $\frac{-1}{2}$ 

= $\frac{-5 x (-1)}{23 x 2}$ 

= $\frac{5}{46}$ 

c) 0,24 x $\frac{-15}{4}$ 

= $\frac{0,24}{1}$ x $\frac{-15}{4}$ 

= $\frac{0,24 x (-15)}{1 x 4}$ 

= $\frac{$\frac{-18}{5}$}{4}$ 

= $\frac{-9}{10}$ 

d) ($\frac{-3}{25}$) : $\frac{-3}{11}$ 

= $\frac{-3}{25}$ x $\frac{-11}{3}$ 

= $\frac{-3 x (-11)}{25 x 3}$ 

= $\frac{33}{75}$ 

= $\frac{11}{25}$ 

e) $\frac{-3}{4}$ x $\frac{12}{-5}$ x ($\frac{-25}{6}$)

= $\frac{-3 x 12 x (-25)}{4 x (-5) x 6}$ 

= $\frac{900}{-120}$ 

= -$\frac{15}{2}$ 

f) (-2) : $\frac{-21}{38}$ x ($\frac{-7}{4}$) x $\frac{3}{-8}$ 

= $\frac{-2}{1}$ x $\frac{-38}{21}$ x $\frac{-7 x 3}{4 x (-8)}$ 

= $\frac{-2 x (-38)}{1 x 21}$ x $\frac{-21}{-32}$ 

= $\frac{76}{21}$ x $\frac{-21}{-32}$ 

= $\frac{76 x (-21)}{21 x (-32)}$ 

= $\frac{-1596}{-672}$ 

= $\frac{19}{8}$ 

g) (-$\frac{7}{23}$) x [(-$\frac{8}{6}$) - $\frac{45}{18}$]

= (-$\frac{7}{23}$) x [(-$\frac{24}{18}$) - $\frac{45}{18}$]

= (-$\frac{7}{23}$) x $\frac{-69}{18}$ 

= $\frac{-7 x (-69)}{23 x 18}$ 

= $\frac{7}{6}$ 

g) ($\frac{11}{12}$ : $\frac{33}{16}$) x $\frac{3}{5}$ 

= ($\frac{11}{12}$ x $\frac{16}{33}$) x $\frac{3}{5}$ 

= $\frac{4}{9}$ x $\frac{3}{5}$ 

= $\frac{4}{15}$ 

Câu 2:

a) $\frac{-11}{23}$ x $\frac{4}{5}$ + (-$\frac{12}{23}$ x $\frac{4}{5}$)

= $\frac{-11}{23}$ x $\frac{4}{5}$ + $\frac{-48}{115}$ 

= $\frac{-44}{115}$ + $\frac{-48}{115}$ 

= $\frac{-4}{5}$ 

b) $\frac{11}{35}$ x $\frac{-2}{5}$ - $\frac{11}{35}$ x $\frac{3}{5}$ 

= $\frac{-22}{175}$ - $\frac{33}{175}$ 

= $\frac{-11}{35}$ 

c) $\frac{-2}{7}$ : $\frac{1}{2}$ - $\frac{-2}{7}$ : $\frac{1}{4}$ 

= $\frac{-4}{7}$ - $\frac{-8}{7}$ 

= $\frac{4}{7}$ 

d) $\frac{-5}{2}$ : $\frac{2}{3}$ + $\frac{-5}{2}$ : $\frac{2}{7}$ 

= $\frac{-15}{4}$ + $\frac{-35}{4}$ 

= $\frac{-25}{2}$ 

e) ($\frac{-2}{3}$ + $\frac{3}{7}$) : $\frac{4}{5}$ + ($\frac{-1}{3}$ + $\frac{4}{7}$) : $\frac{4}{5}$ 

= $\frac{-5}{21}$ : $\frac{4}{5}$ + $\frac{5}{21}$ : $\frac{4}{5}$ 

= $\frac{-25}{84}$ + $\frac{25}{84}$ 

= 0

f) $\frac{5}{9}$ : ($\frac{1}{11}$ - $\frac{5}{22}$) + $\frac{5}{9}$ : ($\frac{1}{15}$ - $\frac{2}{3}$)

= $\frac{5}{9}$ : $\frac{-3}{22}$ + $\frac{5}{9}$ : $\frac{-3}{5}$ 

= $\frac{-110}{27}$ + $\frac{-25}{27}$ 

= -5