We have from the angle bisector theorem that the sides AC and CD are proportional to AB and BD. Hence, we get the following equality that holds in general when the angles BAD and CAD are equal.
[tex] \frac{CD}{AC} = \frac{BD}{AB} [/tex]
Substituting:
[tex] \frac{2}{5.9} = \frac{2.8}{x} \\ x= \frac{5.9*2.8}{2}=8.26=8.3[/tex]
