5/12 x 6/11 + 5/12 x 5/11 + 7/12 giả nhanh giúp mình ạ

$\dfrac{5}{12}$`xx`$\dfrac{6}{11}$`+`$\dfrac{5}{12}$`xx`$\dfrac{5}{11}$`+`$\dfrac{7}{12}$

`=` $\dfrac{5}{12}$`xx`$\left(\dfrac{6}{11}+\dfrac{5}{11}\right)$`+`$\dfrac{7}{12}$

`=` $\dfrac{5}{12}$`xx1+`$\dfrac{7}{12}$

`=` $\dfrac{5}{12}$`+`$\dfrac{7}{12}$

`=` `1`

$\text{$\dfrac{5}{12}$ $\times$ $\dfrac{6}{11}$ + $\dfrac{5}{12}$ $\times$ $\dfrac{5}{11}$ + $\dfrac{7}{12}$}$

$\text{= [ $\dfrac{5}{12}$ $\times$ ( $\dfrac{6}{11}$ + $\dfrac{5}{11}$ ) ] + $\dfrac{7}{12}$}$

$\text{= [ $\dfrac{5}{12}$ $\times$ $\dfrac{6 +5}{11}$ ] + $\dfrac{7}{12}$}$

$\text{= [ $\dfrac{5}{12}$ $\times$ $\dfrac{11}{11}$ ] + $\dfrac{7}{12}$}$

$\text{= [ $\dfrac{5}{12}$ $\times$ 1 ] + $\dfrac{7}{12}$}$

$\text{= $\dfrac{5}{12}$ + $\dfrac{7}{12}$ = $\dfrac{5 + 7}{12}$ = $\dfrac{12}{12}$ = 1}$