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`a)4/5:3/x xx2/11=24/165`
`(4/5xx2/11)xx 3/x=8/55`
`8/55xx3/x=8/55`
`3/x=8/55:8/55`
`3/x=1`
`3:x=1`
`x=3:1`
`x=3`
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`b)4/3:x/5=5/13xx4/9`
`4/3:x/5=20/117`
`x/5=4/3:20/117`
`x/5=39/5`
`x=39`
A) 4/5:3/x X 2/11=24/165
\(\dfrac{4}{5}:\dfrac{3}{x}X\dfrac{2}{11}=\dfrac{24}{165}\)
\(\dfrac{3}{x}=\dfrac{24}{165}:\dfrac{4}{5}:\dfrac{2}{11}\)
\(\dfrac{3}{x}=1\)
\(\dfrac{3}{x}=\dfrac{3}{3}\)
=> x=3
B) \(\dfrac{4}{3}:\dfrac{x}{5}=\dfrac{5}{13}x\dfrac{4}{9}\)
\(\dfrac{4}{3}:\dfrac{x}{5}=\dfrac{20}{117}\)
\(\dfrac{x}{5}=\dfrac{4}{3}:\dfrac{20}{117}\)
\(\dfrac{x}{5}=\dfrac{39}{5}\)
=> x = 39
\(a,\Rightarrow x=\dfrac{7}{3}+\dfrac{6}{7}=\dfrac{49+18}{21}=\dfrac{67}{21}\\ b,\Rightarrow x=\dfrac{15}{7}-\dfrac{13}{14}=\dfrac{30-13}{14}=\dfrac{17}{14}\\ c,\Rightarrow3x=\dfrac{9}{4}-\dfrac{5}{6}=\dfrac{27-10}{12}=\dfrac{17}{12}\\ \Rightarrow x=\dfrac{17}{12}\cdot\dfrac{1}{3}=\dfrac{17}{36}\)
a: 4/5=1-1/5
5/6=1-1/6
mà 1/5>1/6
nên 4/5<5/6
b: 3/7=9/21>5/21
c: 13/12<14/12=7/6
\(\frac{4+a}{13+a}\)= \(\frac{2}{5}\)
\(\frac{2}{5}\) = \(\frac{4+2}{13+2}\)
\(\frac{2}{5}\)= \(\frac{6}{15}\)
Vậy a = 2.
a x 13 = ab
=> a x 13 = 10a + b
=> 13a - 10a = b
=> 3a = b
=> ab = 39
\(\frac{7}{5}-\frac{a}{4}=\frac{13}{20}\)
\(\frac{a}{4}=\frac{7}{5}-\frac{13}{20}\)
\(\frac{a}{4}=\frac{28}{20}-\frac{13}{20}\)
\(\frac{a}{4}=\frac{15}{20}\)
\(\frac{a}{4}=\frac{3}{4}\)
=> a = 3
\(\frac{7}{5}-\frac{a}{4}=\frac{13}{20}\)
\(\frac{a}{4}=\frac{7}{5}-\frac{13}{20}\)
\(\frac{a}{4}=\frac{75}{100}\)
Rút gọn \(\frac{75}{100}=\frac{3}{4}\Rightarrow\)\(\frac{a}{4}\)= \(\frac{3}{4}\)
Vì 3 = 3 Suy ra a = 3