x : 2/5=4/7 : 3/2 12 : x + 2/3= 7/5

Đáp án:

Giải thích các bước giải

1)

 x :  $\dfrac{2}{5}$ =  $\dfrac{4}{7}$ :  $\dfrac{3}{2}$

 x : $\dfrac{2}{5}$ = $\dfrac{8}{21}$

 x = $\dfrac{8}{21}$ × $\dfrac{2}{5}$

 x = $\dfrac{16}{105}$

2)

12 : x + $\dfrac{2}{3}$ = $\dfrac{7}{5}$

12 : x = $\dfrac{7}{5}$ – $\dfrac{2}{3}$

12 : x = $\dfrac{11}{15}$

 x = 12 : $\dfrac{11}{15}$

 x = $\dfrac{180}{11}$