`@` `\text {Ans}`
`\downarrow`
`15/16 \times x = 9/40`
`=> x = 9/40 \div 15/16`
`=> x=9/40 \times 16/15`
`=> x = 6/25`
Vậy, `x=6/25.`
\(\dfrac{15}{16}\times x=\dfrac{9}{40}\\ x=\dfrac{9}{40}:\dfrac{15}{16}\\ x=\dfrac{9}{40}\cdot\dfrac{16}{15}\\ x=\dfrac{144}{600}\\ x=\dfrac{6}{25}\)
\(\Rightarrow x=\dfrac{9}{40}:\dfrac{15}{16}=\dfrac{3.3.4.4}{4.10.3.5}=\dfrac{12}{50}=\dfrac{6}{25}\)