a: \(=\left(-\dfrac{25}{140}+\dfrac{245}{140}+\dfrac{32}{140}\right)\cdot\dfrac{-69}{20}\)

\(=\dfrac{252}{140}\cdot\dfrac{-69}{20}\)

\(=\dfrac{9}{5}\cdot\dfrac{-69}{20}=\dfrac{-621}{100}\)

b: \(=\left(6-2-\dfrac{4}{5}\right)\cdot\dfrac{25}{8}-\dfrac{8}{5}\cdot4\)

\(=\dfrac{16}{5}\cdot\dfrac{25}{8}-\dfrac{32}{5}=\dfrac{18}{5}\)

c: \(=\left(\dfrac{2}{24}+\dfrac{18}{24}+\dfrac{14}{24}\right):\dfrac{-17}{8}\)

\(=\dfrac{34}{24}\cdot\dfrac{-8}{17}=\dfrac{-1}{3}\cdot2=-\dfrac{2}{3}\)

â, -4/9(7/15+8/15)=-4/9

b,-5/4(16/25+9/25)=-5/4

,..... 

dài quá mik làm ko hết 

hok tốt

a)\(\frac{-4}{9}\times\frac{7}{15}+\frac{-4}{9}\times\frac{8}{15}\)

= \(\frac{-4}{9}\times\left(\frac{7}{15}+\frac{8}{15}\right)\)

=\(-\frac49\times1\)

=\(-\frac49\)

\(A=-1-4=-5\)

\(B=\frac{4}{3}.\frac{15}{7}-16\)

\(B=\frac{20}{7}-16\)

\(B=\frac{-92}{7}\)

\(C=\frac{28}{15}.0,25.3+\left(\frac{8}{15}-\frac{1}{4}\right)\div1\frac{23}{24}\)

\(C=1,4+\frac{17}{60}\div\frac{47}{24}\)

\(C=1,4+\frac{34}{235}\)

\(C=\frac{363}{235}\)

\(A=\frac{-15}{8}+\frac{7}{8}-4\)

\(=-1-4=-5\)

\(B=\left(4-2\frac{2}{3}\right).2\frac{1}{7}-1\frac{3}{5}:\frac{1}{10}\)

\(=\frac{4}{3}.\frac{15}{7}-\frac{8}{5}:\frac{1}{10}\)

\(=\frac{20}{7}-16=\frac{-92}{7}\)

\(C=1\frac{13}{15}.\left(0,5\right)^2.3+\left(\frac{8}{15}-25\%\right):1\frac{23}{24}\)

\(=\frac{28}{15}.\frac{1}{4}.3+\frac{17}{60}:\frac{47}{24}\)

\(=\frac{7}{15}.3+\frac{17}{60}:\frac{47}{24}\)

\(=\frac{7}{5}+\frac{34}{235}=\frac{363}{235}\)

49\(\frac{8}{23}\) - (5\(\frac{7}{32}\) + 14\(\frac{8}{23}\))

= 49\(\frac{8}{23}\) - 5\(\frac{7}{32}\) - 14\(\frac{8}{23}\)

= (49\(\frac{8}{23}\) - 14\(\frac{8}{23}\)) - 5\(\frac{7}{32}\)

= 35 - 5 - \(\frac{7}{32}\)

= 30 - \(\frac{7}{32}\)

= \(\frac{960}{32}\) - \(\frac{7}{32}\)

= 953/32

Câu b:

71\(\frac{38}{45}\) - (43\(\frac{8}{45}\) - 1\(\frac{17}{57}\))

= 71\(\frac{38}{45}\) - 43\(\frac{8}{45}\) - 1\(\frac{17}{57}\)

= 28\(\frac{30}{45}\) - 1\(\frac{17}{57}\)

= 28\(\frac23\) - 1\(\frac{17}{57}\)

= \(\frac{86}{3}\) - \(\frac{74}{57}\)

= \(\frac{1634}{57}\) - \(\frac{74}{57}\)

= \(\frac{1560}{57}\)

= \(\frac{520}{19}\)

B)

a) \(\frac{-3}{7}+\frac{15}{26}-\left(\frac{2}{13}-\frac{3}{7}\right)=\frac{-3}{7}+\frac{15}{26}-\frac{2}{13}+\frac{3}{7}=\left(\frac{-3}{7}+\frac{3}{7}\right)+\left(\frac{15}{26}-\frac{2}{13}\right)\)

\(=\frac{15-4}{26}=\frac{11}{26}\)

c) \(\frac{-11}{23}.\frac{6}{7}+\frac{8}{7}.\frac{-11}{23}-\frac{1}{23}=\frac{-11}{23}.\left(\frac{6}{7}+\frac{8}{7}\right)-\frac{1}{23}\)

\(=\frac{-11}{23}.2-\frac{1}{23}=\frac{-22-1}{23}=\frac{-23}{23}=-1\)

1. a) \(\frac{-2}{7}+\frac{15}{23}+\frac{\left(-15\right)}{17}+\frac{4}{19}+\frac{8}{23}\)

    \(=\left(\frac{-2}{7}+\frac{-5}{7}\right)+\left(\frac{15}{23}+\frac{8}{23}\right)+\frac{4}{19}\)

    \(=\left(-1\right)+1+\frac{4}{19}\)

    \(=0+\frac{4}{19}=\frac{4}{19}\)

b) \(\frac{7}{19}\cdot\frac{8}{11}+\frac{7}{19}\cdot\frac{3}{11}+\frac{12}{19}\)

   \(=\frac{7}{19}\cdot\left(\frac{8}{11}+\frac{3}{11}\right)+\frac{12}{19}\)

   \(=\frac{7}{19}\cdot1+\frac{12}{19}\)

   \(=\frac{7}{19}+\frac{12}{19}=\frac{19}{19}=1\)

2. a) \(\frac{1}{3}+\frac{\left(-2\right)}{16}-\frac{7}{14}\)

\(=\frac{5}{24}-\frac{1}{2}\)

\(=-\frac{7}{24}\)

b) \(11\frac{3}{13}-2\frac{4}{7}+5\frac{3}{13}\)

\(=\left(11-2+5\right)+\frac{3}{13}-\frac{4}{7}+\frac{3}{13}\)

\(=14+\left(-\frac{10}{91}\right)\)

\(=-14\frac{10}{91}\)

c) \(0,7\cdot2\frac{2}{3}\cdot20\cdot0,375\cdot\frac{5}{28}\)

\(=\frac{7}{10}\cdot\frac{8}{3}\cdot20\cdot\frac{3}{8}\cdot\frac{5}{28}\)

\(=\left(\frac{7}{10}\cdot\frac{5}{28}\right)\cdot\left(\frac{8}{3}\cdot\frac{3}{8}\right)\cdot20\)

\(=\frac{1}{8}\cdot1\cdot20\)

\(=\frac{20}{8}=\frac{5}{2}\)

d) \(\frac{6}{7}+\frac{5}{7}:5-\frac{8}{9}\)

\(=\frac{6}{7}+\frac{1}{7}-\frac{8}{9}\)

\(=1-\frac{8}{9}\)

\(=\frac{1}{9}\)

~Học tốt~

a. \(\frac{-3}{7}+\frac{15}{26}-\left(\frac{2}{13}-\frac{3}{7}\right)=\frac{-3}{7}+\frac{15}{26}-\frac{2}{13}+\frac{3}{7}=\frac{15}{13.2}-\frac{2}{13}=\frac{15}{13.2}-\frac{2.2}{13.2}=\frac{15-4}{26}=\frac{11}{26}\)

C. \(\frac{-11}{23}.\frac{6}{7}+\frac{8}{7}.\frac{-11}{23}-\frac{1}{23}=\frac{1}{23}.\left(-11.\frac{6}{7}-11.\frac{8}{7}-1\right)=\frac{1}{23}.\left(-22-1\right)=\frac{1}{23}.\left(-23\right)=-1\)