Bài II x/6 = -14/4 + 40/15 Bài III 1) 10/144 + -2/135 + 11/120 2) 1/3 + -2/5 + 1/6 + -1/5< -3/4 + 2/7 + -1/4 + 3/5 + 5/7

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 $\frac{1}{3}+\frac{-2}{5}+\frac{1}{6}+\frac{-1}{5}$ < $\frac{-3}{4}+\frac{2}{7}+\frac{-1}{4}+\frac{3}{5}+\frac{5}{7}$