$\Delta$ ABC, AD phân giác
=> $\frac{AB}{AC}= \frac{BD}{DC}$
$\Leftrightarrow \frac{AB}{BD}= \frac{AC}{DC}= \frac{AB+AC}{BD+DC}= \frac{AB+AC}{BC}= 1,4$
=> BD= $\frac{AB}{1,4}$= $\frac{75}{7}$
CD= $\frac{AC}{1,4}$= $\frac{100}{7}$
$\frac{S_{ABD}}{S_{ADC}}= \frac{0,5AH.BD}{0,5AH.CD}= \frac{BD}{CD}= \frac{3}{4}$