[tex]\bigtriangleup ABD \cong\bigtriangleup BCD\Rightarrow \frac{BD}{7} = \frac{18}{BD} \Leftrightarrow {BD}^{2} = 126\Leftrightarrow BD = 3 \sqrt{14} \\ BC = \sqrt{{BD}^{2} + {CD}^{2} } = \sqrt{ {3 \sqrt{14} }^{2} + {7}^{2} } = \sqrt{126 + 49 } = \sqrt{175} \approx 13.2 \\ \Rightarrow B. \: 13.2[/tex]
