Bài 1:
6) (-$\frac{1}{3}$ + $\frac{7}{13}$) - (-$\frac{16}{24}$ + $\frac{6}{26}$ + $\frac{9}{13}$)
= $\frac{8}{39}$ - $\frac{10}{39}$
= -$\frac{2}{39}$
7) -$\frac{7}{3}$ - [$\frac{2}{5}$ - ($\frac{1}{3}$ + $\frac{-5}{25}$)]
= -$\frac{7}{3}$ - ($\frac{2}{5}$ - $\frac{2}{15}$)
= -$\frac{7}{3}$ - $\frac{4}{15}$
= -$\frac{13}{5}$
8) (2$\frac{1}{4}$ - 3$\frac{1}{5}$) - [-$\frac{3}{4}$ + ($\frac{4}{5}$ - 2019)]
= ($\frac{9}{4}$ - $\frac{16}{5}$) - (-$\frac{3}{4}$ + $\frac{-10091}{5}$)
= -$\frac{19}{20}$ - $\frac{-40379}{20}$
= 2018
Bài 2:
1) $\frac{3}{5}$ + x - $\frac{1}{5}$ = $\frac{2}{3}$
$\frac{3}{5}$ + x = $\frac{2}{3}$ + $\frac{1}{5}$
$\frac{3}{5}$ + x = $\frac{13}{15}$
x = $\frac{13}{15}$ - $\frac{3}{5}$
x = $\frac{4}{15}$
2) -x + $\frac{1}{2}$ = $\frac{3}{4}$ - (-$\frac{1}{2}$)
-x + $\frac{1}{2}$= $\frac{5}{4}$
-x = $\frac{5}{4}$ - $\frac{1}{2}$
x = $\frac{3}{4}$
3) ($\frac{4}{7}$ - x) - $\frac{1}{3}$ = - (-$\frac{2}{5}$)
($\frac{4}{7}$ - x) - $\frac{1}{3}$ = $\frac{2}{5}$
($\frac{4}{7}$ - x) = $\frac{2}{5}$ + $\frac{1}{3}$
$\frac{4}{7}$ - x = $\frac{11}{15}$
x = $\frac{4}{7}$ - $\frac{11}{15}$
x = -$\frac{17}{105}$
4) $\frac{7}{20}$ - ($\frac{2}{5}$ + x) = $\frac{1}{6}$
($\frac{2}{5}$ + x)= $\frac{7}{20}$ - $\frac{1}{6}$
$\frac{2}{5}$ + x = $\frac{11}{60}$
x = $\frac{11}{60}$ - $\frac{2}{5}$
x = -$\frac{13}{60}$
