\(a,\dfrac{x}{y}=\dfrac{8}{15}:\dfrac{2}{3}\\ \dfrac{x}{y}=\dfrac{4}{5}\\ =>x=4;y=5\\ b,\dfrac{x}{y}=\dfrac{2}{5}.\dfrac{3}{4}\\ \dfrac{x}{y}=\dfrac{3}{10}\\ =>x=3;y=10\\ c,\dfrac{x}{y}=\dfrac{3}{5}:\dfrac{4}{7}\\ \dfrac{x}{y}=\dfrac{21}{20}\\ =>x=21;y=20\)
`2/3 . x/y = 8/15`
`x/y=8/15:2/3`
`x/y=8/15 . 3/2`
`x/y =4/5`
Vậy `x/y=4/5`
____________________________
`x/y :3/4=2/5`
`x/y = 2/5 xx 3/4`
`x/y =3/10`
Vậy `x/y=3/10`
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`3/5 : x/y=4/7`
`x/y=3/5:4/7`
`x/y = 3/5 . 7/4`
`x/y=21/20`
Vậy `x/y=21/20`
a thì 8/5 : 2/3
b lấy 2/5 * 3/4
c lấy 3/5 : 4/7
