[填空题]
The following diagram g/rd 8w 3r(vdhshows trianglf 4brs.2ygt sig0-d /g4 syp9pe A B C . Point D lies on [A C] so that [DB] bisect2 y. -ygd0b fgp 49gps/4rtisss CEAA. The area of the triangle A B C is 3$ \mathrm{~cm}^{2}$ .
$\mathrm{AB}=2 \sqrt{7} \mathrm{~cm}, \mathrm{BC}=x \mathrm{~cm}$ , and $\mathrm{CBD}=\theta$ , where $ \sin \theta=\frac{3}{4} $ Find the value of x in the form of $ \frac{a}{b}$ where a and b are positive integers. x =
