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a: =>4/9*a/b=5/27+3/27=8/27
=>a/bb=8/27:4/9=8/27*9/4=72/108=2/3
b: =>9/13*a/b=40/91+1/7=53/91
=>a/b=53/63
`a)4/9xxa/b-1/9=5/27`
`=>4/9xxa/b=5/27+1/9`
`=>4/9xxa/b=5/27+3/27`
`=>4/9xxa/b=8/27`
`=>a/b=8/27:4/9`
`=>a/b=8/27xx9/4`
`=>a/b=2/3`
Vậy `a=2` và `b=3`
__
`b)9/13xxa/b+1/7=40/91`
`=>9/13xxa/b=40/91-1/7`
`=>9/13xxa/b=40/91-13/91`
`=>9/13xxa/b=27/91`
`=>a/b=27/91:9/13`
`=>a/b=27/91xx13/9`
`=>a/b=39/91`
Vậy `a=39` và `b=91`
\(\frac{7}{5}-\frac{a}{4}=\frac{13}{20}\)
\(\frac{a}{4}=\frac{7}{5}-\frac{13}{20}\)
\(\frac{a}{4}=\frac{28}{20}-\frac{13}{20}\)
\(\frac{a}{4}=\frac{15}{20}\)
\(\frac{a}{4}=\frac{3}{4}\)
=> 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
a.
x/y x 3/4 = 5/6 + 1/3
x/y x 3/4 = 7/6
x/y = 7/6 : 3/4
x/y = 14/9
b.
7/9 : x/y = 10/7 - 13/14
7/9 : x/y = 1/2
x/y = 7/9 : 1/2
x/y = 14/9
cho 1 k nha bn
a) 9/7:x=3/4
x=9/7:3/4
x=12/7
b) x-1/6=13/4-5/2
x-1/6=3/4
x=3/4+1/6
x=11/12
\(a.\dfrac{12+x}{42}=\dfrac{35}{42}\Leftrightarrow12+x=35\Leftrightarrow x=23\)
\(b.\dfrac{25-x}{40}=\dfrac{3}{8}\Leftrightarrow\dfrac{25-x}{40}=\dfrac{15}{40}\Leftrightarrow25-x=15\Leftrightarrow x=10\)
\(c.\dfrac{13+x}{20}=\dfrac{3}{4}\Leftrightarrow\dfrac{13+x}{20}=\dfrac{15}{20}\Leftrightarrow13+x=15\Leftrightarrow x=2\)
\(d.\dfrac{23-x}{25}=\dfrac{20}{25}\Leftrightarrow23-x=20\Leftrightarrow x=3\)
`7/5 - a/4 = 13/20`
`=> a/4 = 7/5 - 13/20`
`=> a/4 = 3/4`
`=> a = 3`
Vậy `a = 3`