câu đố:

có một con chim đậu trên cành 2con khác bay  đến đậu.Hỏi trên cành có bao nhiêu con chim?

A) \(\frac{1}{2}\cdot\left(\frac{2}{9}+\frac{3}{7}-\frac{5}{27}\right)\) 

\(=\frac{1}{2}\cdot\frac{1}{2}\)

\(=\frac{1}{4}\)

B)   \(\left(\frac{-5}{28}+1.75+\frac{8}{35}\right):\left(-3\frac{9}{20}\right)\)

\(=\left(\frac{-5}{28}+\frac{7}{4}+\frac{8}{35}\right):\frac{-69}{20}\)

\(=\frac{14}{5}:\frac{-69}{20}\)

\(=\frac{-56}{69}\)

a.-1,75-(-\(\dfrac{1}{9}\)-2\(\dfrac{1}{8}\))
-1,75-\(\dfrac{1}{9}+\dfrac{17}{8}\)
\(-\dfrac{7}{4}-\dfrac{1}{9}+\dfrac{17}{8}\)
\(\dfrac{-126}{72}-\dfrac{8}{72}+\dfrac{153}{72}\)
=\(\dfrac{19}{72}\)

b.\(\dfrac{-1}{12}-\left(2\dfrac{5}{8}-\dfrac{1}{3}\right)\)
\(\dfrac{-1}{12}-\left(\dfrac{21}{8}-\dfrac{1}{3}\right)\)
\(\dfrac{-1}{12}-\dfrac{21}{8}+\dfrac{1}{3}\)
\(\dfrac{-2}{24}-\dfrac{63}{24}+\dfrac{64}{24}\)
=\(\dfrac{-1}{24}\)

\(\dfrac{-5}{6}-\left(\dfrac{-3}{8}+\dfrac{1}{10}\right)\)
\(\dfrac{-5}{6}-\dfrac{-3}{8}-\dfrac{1}{10}\)
 

a) \(\dfrac{1}{2}.\left(\dfrac{2}{9}+\dfrac{3}{7}-\dfrac{5}{27}\right)\)

\(=\dfrac{1}{2}.\left(\dfrac{41}{63}-\dfrac{5}{27}\right)\)

\(=\dfrac{1}{2}.\dfrac{88}{189}\)

\(=\dfrac{44}{189}\)

b) \(\left(\dfrac{-5}{28}+1,75+\dfrac{8}{35}\right):\left(-3\dfrac{9}{20}\right)\)

\(=\left(\dfrac{11}{7}+\dfrac{8}{35}\right):\left(-3\dfrac{9}{20}\right)\)

\(=\dfrac{9}{5}:\left(-3\dfrac{9}{20}\right)\)

\(=\dfrac{9}{5}:\dfrac{-69}{20}\)

\(=\dfrac{-12}{23}\)

c) \(\dfrac{1}{3}.\dfrac{5}{7}-\dfrac{7}{27}.\dfrac{36}{14}\)

\(=\dfrac{5}{21}-\dfrac{7}{27}.\dfrac{36}{14}\)

\(=\dfrac{5}{21}-\dfrac{2}{3}\)

\(=\dfrac{-3}{7}\)

d) \(70,5-528:\dfrac{15}{2}\)

\(=70,5-\dfrac{352}{5}\)

\(=\dfrac{1}{10}\)

em không trả lời được câu hỏi của chị nhưng chị có thể giúp em đăng bài toán lên bằng cách nào không

c.

\(\frac{1}{3}\times\frac{5}{7}-\frac{7}{27}\times\frac{36}{14}\)

\(=\frac{1}{3}\times\frac{5}{7}-\frac{7}{3\times9}\times\frac{4\times9}{7\times2}\)

\(=\frac{1}{3}\times\frac{5}{7}-\frac{1}{3}\times\frac{4}{6}\)

\(=\frac{1}{3}\times\left(\frac{5}{7}-\frac{4}{6}\right)\)

\(=\frac{1}{3}\times\left(\frac{30-38}{42}\right)\)

\(=\frac{1}{3}\times\frac{-8}{42}\)

\(=-\frac{4}{63}\)

Chúc bạn học tốt

Sorry nha, tại mik làm biếng quá

d.

\(70,5-528\div\frac{15}{2}\)

\(=70,5-528\div7,5\)

\(=70,5-70,4\)

\(=0,1\)

Chúc bạn học tốt

b/\(1\frac{2}{9}\)

Bài 1:

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

\(=-\frac{3}{7}+\frac{15}{26}-\frac{4}{26}+\frac{3}{7}\)

\(=\left(-\frac{3}{7}+\frac{3}{7}\right)+\left(\frac{15}{26}-\frac{4}{26}\right)\)

\(=0+\frac{11}{26}\)

\(=\frac{11}{26}\)

b)\(2\frac{3}{7}+\frac{2}{9}-1\frac{3}{7}\)

\(=\frac{17}{7}+\frac{2}{9}-\frac{10}{7}\)

\(=\left(\frac{17}{7}-\frac{10}{7}\right)+\frac{2}{9}\)

\(=1+\frac{2}{9}\)

\(=1\frac{2}{9}=\frac{11}{9}\)

c)\(\left(\frac{377}{-231}-\frac{124}{89}+\frac{34}{791}\right).\left(\frac{1}{6}-\frac{1}{8}-\frac{1}{24}\right)\)

\(=\left(\frac{377}{-231}-\frac{124}{89}+\frac{34}{791}\right).\left(\frac{4}{24}-\frac{3}{24}-\frac{1}{24}\right)\)

\(=\left(\frac{377}{-231}-\frac{124}{89}+\frac{34}{791}\right).0\)

\(=0\)

\(B1:\)  \(a,\frac{-3}{7}+\frac{15}{26}-\frac{2}{13}+\frac{3}{7}\)

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

= \(\frac{11}{26}+0=\frac{11}{26}\)

\(b,2\frac{3}{7}-1\frac{3}{7}+\frac{2}{9}\)

= \(1+\frac{2}{9}=1\frac{2}{9}\)

\(c,\left(\frac{377}{-231}-\frac{124}{89}+\frac{34}{791}\right).\left(\frac{4}{24}-\frac{3}{24}-\frac{1}{24}\right)\)

= \(\left(\frac{377}{-231}-\frac{124}{89}+\frac{34}{791}\right).0=0\)

\(B2:\)\(a,\frac{1}{2}.\left(\frac{2}{9}+\frac{3}{12}-\frac{5}{27}\right)\)

= \(\frac{1}{2}.\left(\frac{17}{36}-\frac{5}{27}\right)\)

= \(\frac{1}{2}.\left(\frac{31}{108}\right)\)

= \(\frac{31}{216}\)

b, \(\left(1\frac{4}{5}\right):-3\frac{9}{20}\)

= \(\frac{-12}{23}\)

c, \(\frac{5}{21}-2\frac{11}{14}\)

= \(-2\frac{23}{42}\)

d, \(70\frac{1}{2}-70\frac{2}{5}\)

= \(1\frac{1}{704}\)

B1:

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

\(\Rightarrow\frac{-3}{7}+\frac{15}{26}-\frac{2}{13}+\frac{3}{7}\)

\(\Rightarrow\left(\frac{-3}{7}+\frac{3}{7}\right)+\frac{15}{26}-\frac{4}{26}\)

\(\Rightarrow\frac{15}{26}-\frac{4}{26}\)

=\(\frac{11}{26}\)

b,\(\frac{23}{7}+\frac{2}{9}-\frac{13}{7}\)

\(=\frac{23}{7}-\frac{13}{7}+\frac{2}{9}\)

\(=\frac{10}{7}+\frac{2}{9}\)

\(=\frac{104}{63}\)

c,\(\left(\frac{377}{-231}-\frac{124}{89}+\frac{34}{791}\right).\left(\frac{1}{6}-\frac{1}{8}-\frac{1}{24}\right)\)

\(=\left(\frac{377}{-231}-\frac{124}{89}+\frac{34}{791}\right).0\)

\(=0\)

a: \(=\dfrac{-3}{7}+\dfrac{15}{26}-\dfrac{2}{13}+\dfrac{3}{7}=\dfrac{15}{26}-\dfrac{4}{26}=\dfrac{11}{26}\)

b: \(=\dfrac{6}{7}+\dfrac{2}{9}-\dfrac{10}{7}-5=\dfrac{-4}{7}-5+\dfrac{2}{9}=-\dfrac{337}{63}\)

c: \(=-\dfrac{11}{23}\left(\dfrac{6}{7}+\dfrac{8}{7}\right)-\dfrac{1}{23}=\dfrac{-22}{23}-\dfrac{1}{23}=-1\)