Answer:
[tex] x = \sqrt{30}[/tex]
Step-by-step explanation:
By Geometric Mean Property:
[tex]BD = \sqrt{7 \times 3} \\ \\ BD = \sqrt{21} \\ \\ In \: right\: \triangle BDC \\ \\ By \: Pythagoras \: Theorem \\ \\ {x}^{2} = { \sqrt{21} }^{2} + {3}^{2} \\ \\ {x}^{2} =21 + 9\\ \\ {x}^{2} =30 \\ \\ \huge \purple{x = \sqrt{30} }[/tex]
