Bài II:
$\frac{x}{6}=\frac{-14}{4}+\frac{40}{15}$
$⇒\frac{x}{6}=\frac{-7}{2}+\frac{8}{3}$
$⇒\frac{x}{6}=\frac{-21}{6}+\frac{16}{6}$
$⇒\frac{x}{6}=\frac{-5}{6}$
$⇒6.x= -5.6$
$⇒6x = -30$
$⇒x = -5$
Vậy $x = -5$
Bài III:
1) $\frac{10}{144}+\frac{-2}{135}+\frac{11}{120}$
$=\frac{5}{72}+\frac{-2}{135}+\frac{11}{120}$
$=\frac{1125}{16200}+\frac{-240}{16200}+\frac{1485}{16200}$
$=\frac{1125 - 240 + 1485}{16200}$
$=\frac{2370}{16200}$
$=\frac{79}{540}$
2) Vế trái = $\frac{1}{3}+\frac{-2}{5}+\frac{1}{6}+\frac{-1}{5}$
$=\frac{-3}{5}+\frac{1}{2}$
$=\frac{-1}{10}$
Vế phải = $\frac{-3}{4}+\frac{2}{7}+\frac{-1}{4}+\frac{3}{5}+\frac{5}{7}$
$ = -1 + 1 + \frac{3}{5}$
$ = \frac{3}{5}$
⇒ Vế trái < vế phải hay $\frac{1}{3}+\frac{-2}{5}+\frac{1}{6}+\frac{-1}{5}$ < $\frac{-3}{4}+\frac{2}{7}+\frac{-1}{4}+\frac{3}{5}+\frac{5}{7}$
