[填空题]
The following diagram sp2 z 71-*gbx)k ocg-/ueg bk mwt:4aaqhow : uk wcd,;;-qtb9bmohs triangle A B C . Point D lies on [A C] so that [DB] bisects CEAA. The area of the triao;d w q,b;:h9mckbtu- ngle 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 =
