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Bài làm:
a) \(\left(\frac{2x}{7}-5\right)\div\left(-8\right)=0,75\)
\(\Leftrightarrow\frac{2x}{7}-5=-6\)
\(\Leftrightarrow\frac{2x}{7}=-1\)
\(\Leftrightarrow x=-\frac{7}{2}\)
b) \(\frac{11}{13}-\left(\frac{5}{42}-x\right)=-\left(\frac{15}{28}-\frac{11}{13}\right)\)
\(\Leftrightarrow x+\frac{11}{13}-\frac{5}{42}=\frac{11}{13}-\frac{15}{28}\)
\(\Rightarrow x=-\frac{5}{7}\)
=28/15*3/4-(104/195+1/4)*24/47-(1+4/13)
=7/5-2/5-1-4/13
=-4/13
=28/15 . 3/4 - 4/5 : 7/5
= 7/5 - 4/5 x 5/7
= 7/5 - 4/7
= 49/35 - 20/35
= 29/35
`1 13/15 . 0,75 - (11/20 + 25%) : 1 2/5`
=` 28/15 . 3/4 - (11/20 + 1/4) . 75/7`
= `7/5 - 4/5 . 57 `
= `7/5 - 4/7`
= `29/35`
\(1\dfrac{13}{15}.0,75-\left(\dfrac{8}{15}+25\%\right).\dfrac{24}{47}-3\dfrac{12}{13}:3\)
\(=\dfrac{28}{15}.\dfrac{3}{4}-\left(\dfrac{8}{15}+\dfrac{1}{4}\right).\dfrac{24}{47}-\dfrac{51}{13}:3\)
\(=\dfrac{7}{5}-\dfrac{47}{60}.\dfrac{24}{47}-\dfrac{17}{13}\)
\(=\dfrac{7}{5}-\dfrac{2}{5}-\dfrac{17}{13}\)
\(=1-\dfrac{17}{13}=-\dfrac{4}{13}\)
\(1\frac{13}{15}.0,75-\left(\frac{11}{20}+\frac{25}{100}\right):\frac{7}{5}\)
\(=\frac{28}{15}.\frac{3}{4}-\frac{4}{5}:\frac{7}{5}\)
\(=\frac{7}{5}-\frac{4}{7}\)
\(=\frac{29}{35}\)
\(1\frac{13}{15}\cdot0,75-\left(\frac{11}{20}+\frac{25}{100}\right):\frac{7}{5}\)
\(=\frac{28}{15}\cdot\frac{3}{4}-\frac{4}{5}:\frac{7}{5}\)
\(=\frac{7}{5}-\frac{4}{7}\)
\(=\frac{29}{35}\)
\(1\frac{13}{15}.0,75-\left(\frac{11}{20}+25\%\right):\frac{7}{3}\)
\(=\frac{28}{15}.\frac{3}{4}-\left(\frac{11}{20}+\frac{1}{4}\right):\frac{7}{3}\)
\(=\frac{7}{5}-\frac{4}{5}.\frac{3}{7}\)
\(=\frac{7}{5}-\frac{12}{35}\)
\(=\frac{37}{35}\)
Đặt A=\(1\frac{13}{15}\). \(0,75\) - (\(\frac{11}{20}\)+25%):\(\frac{7}{3}\)
A=\(\frac{28}{15}\). \(\frac{3}{4}\)-(\(\frac{11}{20}\)+\(\frac{1}{4}\)). \(\frac{3}{7}\)
A=\(\frac{7}{5}\)- \(\frac{4}{5}\).\(\frac{3}{7}\)
A=\(\frac{7}{5}\)-\(\frac{12}{35}\)
A=\(\frac{37}{35}\)
\(1\dfrac{13}{15}\cdot0,75\cdot\left(\dfrac{8}{15}+0.25\right)\cdot\dfrac{24}{47}\)
= \(\dfrac{28}{15}\cdot\dfrac{3}{4}\cdot\left(\dfrac{8}{15}+\dfrac{1}{4}\right)\cdot\dfrac{24}{47}\)
= \(\dfrac{7}{5}\cdot\dfrac{47}{60}\cdot\dfrac{24}{47}\)
\(=\dfrac{329}{300}\cdot\dfrac{24}{47}\)
\(=\dfrac{14}{25}\)
=0,65
\(\dfrac{13}{15}\) x 0,75 = \(\dfrac{13}{15}\) x \(\dfrac{3}{4}\)
= \(\dfrac{39}{60}\)