2 câu trả lời
$\dfrac{-18}{24}$ `-` `15/21`
`=` $\dfrac{-18.7}{24.7}$ `-` $\dfrac{15.8}{21.8}$
`=` $\dfrac{-126}{168}$ `-` $\dfrac{120}{168}$
`=` $\dfrac{-126-120}{168}$
`=` $\dfrac{-246}{168}$
`=` $\dfrac{-41}{28}$
$\dfrac{-18}{24}$ `-` `15/21`
`=` $\dfrac{-18.7}{24.7}$ `-` $\dfrac{15.8}{21.8}$
`=` $\dfrac{-126}{168}$ `-` $\dfrac{120}{168}$
`=` $\dfrac{-126-120}{168}$
`=` $\dfrac{-246}{168}$
`=` $\dfrac{-41}{28}$