[填空题]
The following diagram s)myaf ps2ek 7ny+j.c,*bj8mwhows triang pmkl,5jf3bfu) +90 f, 3axxt fibwh)qle $ \mathrm{ABC}$ . Point $\mathrm{D}$ lies on [AC] so that [DB] bisects CBEA. 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 $\mathrm{CB} \mathrm{D}=\theta$ , 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.
