Bài 4.
a.
$\frac{5}{4}+\frac{-1}{2}-\frac{7}{8}$
$=\frac{10}{8}-\frac{4}{8}-\frac{7}{8}=\frac{10-4-7}{8}=\frac{-1}{8}$
b.
\(=\left(\frac{15}{24}-\frac{6}{24}+\frac{14}{24}\right):\frac{-5}{4}=\frac{15-6+14}{24}.\frac{-4}{5}\)
\(=\frac{23}{24}.\frac{-4}{5}=\frac{-23}{30}\)
c.
\(=\frac{21}{5}+\frac{5}{14}.\frac{14}{15}=\frac{21}{5}+\frac{1}{3}=\frac{63}{15}+\frac{5}{15}=\frac{68}{15}\)
d.
\(=\frac{-10}{10}+\frac{-1}{6}.\frac{7}{3}+\frac{37}{18}\)
\(=-1-\frac{7}{18}+\frac{37}{18}=-1+\frac{30}{18}=-1+\frac{5}{3}=\frac{-3+5}{3}=\frac{2}{3}\)
Bài 5.
a.
$x=\frac{-5}{6}-\frac{-2}{3}=\frac{-5}{6}+\frac{2}{3}$
$x=\frac{-5}{6}+\frac{4}{6}=\frac{-1}{6}$
b.
$x:\frac{1}{3}=-9\frac{1}{2}-\frac{1}{4}$
$x:\frac{1}{3}=\frac{-39}{4}$
$x=\frac{-39}{4}.\frac{1}{3}=\frac{-13}{4}$
c.
$\frac{x}{17}-\frac{9}{34}=\frac{5}{2}$
$\frac{x}{17}=\frac{5}{2}+\frac{9}{34}=\frac{47}{17}$
$x=47$
d.
$\frac{2}{3}x.\frac{3}{4}-\frac{1}{2}.\frac{3}{4}-\frac{2}{5}x=\frac{17}{4}$
$\frac{1}{2}x-\frac{3}{8}-\frac{2}{5}x=\frac{17}{4}$
$\frac{1}{10}x-\frac{3}{8}=\frac{17}{4}$
$\frac{1}{10}x=\frac{3}{8}+\frac{17}{4}=\frac{37}{8}$
$x=\frac{370}{8}=\frac{185}{4}$