a. -5/7×2/11+ -5/7×9/11+12/7 b.-4/5×1/2+ -4/5×1/3- -4/5÷1/4 c.1/4+3/4×(-1/2+2/3 d.2/5-3/4-1/2 e.7/2- 50/100 f.8/15× -9/14+8/15× -5/14 g.-3/7+5/13+ -4/

a, $\frac{-5}{7}$ x $\frac{2}{11}$ + $\frac{-5}{7}$ x $\frac{9}{11}$ + $\frac{12}{7}$

= $\frac{-5}{7}$ x ($\frac{2}{11}$ + $\frac{9}{11}$) + $\frac{12}{7}$

= $\frac{-5}{7}$ x 1 + $\frac{12}{7}$

= $\frac{-5}{7}$ + $\frac{12}{7}$

= $\frac{7}{7}$

= 1

b, $\frac{-4}{5}$ x $\frac{1}{2}$ + $\frac{-4}{5}$ x $\frac{1}{3}$ – $\frac{-4}{5}$ : $\frac{1}{4}$

= $\frac{-4}{5}$ x $\frac{1}{2}$ + $\frac{-4}{5}$ x $\frac{1}{3}$ – $\frac{-4}{5}$ x 4

= $\frac{-4}{5}$ x ($\frac{1}{2}$ + $\frac{1}{3}$ – 4)

= $\frac{-4}{5}$ x $\frac{-19}{6}$

= $\frac{38}{15}$

c, $\frac{1}{4}$ + $\frac{3}{4}$ x (-$\frac{1}{2}$ + $\frac{2}{3}$)

= $\frac{1}{4}$ + $\frac{3}{4}$ x ($\frac{-3}{6}$ + $\frac{4}{6}$)

= $\frac{1}{4}$ + $\frac{3}{4}$ x $\frac{1}{6}$

= $\frac{1}{4}$ + $\frac{1}{8}$

= $\frac{2}{8}$ + $\frac{1}{8}$

= $\frac{3}{8}$

d, $\frac{2}{5}$ – $\frac{3}{4}$ – $\frac{1}{2}$

= $\frac{8}{20}$ – $\frac{15}{20}$ – $\frac{10}{20}$

= -$\frac{17}{20}$

e, $\frac{7}{2}$ – $\frac{50}{100}$

= $\frac{7}{2}$ – $\frac{1}{2}$

= $\frac{6}{2}$

= 3

f, $\frac{8}{15}$ x $\frac{-9}{14}$ + $\frac{8}{15}$ x $\frac{-5}{14}$

= $\frac{8}{15}$ x ($\frac{-9}{14}$ – $\frac{5}{14}$)

= $\frac{8}{15}$ x (-1)

= -$\frac{8}{15}$

g, $\frac{-3}{7}$ + $\frac{5}{13}$ – $\frac{4}{7}$

= ($\frac{-3}{7}$ – $\frac{4}{7}$) + $\frac{5}{13}$

= -1 + $\frac{5}{13}$

= -1$\frac{5}{13}$

= $\frac{-8}{13}$

h, $\frac{146}{13}$ – ($\frac{18}{7}$ + $\frac{68}{13}$)

= $\frac{146}{13}$ – $\frac{18}{7}$ – $\frac{68}{13}$

= ($\frac{146}{13}$ – $\frac{68}{13}$) – $\frac{18}{7}$

= 6 – $\frac{18}{7}$

= $\frac{42}{7}$ – $\frac{18}{7}$

= $\frac{24}{7}$

(Cho mk ctlhn nha, thanks ^.^

Chúc bạn học tốt !!!)