По теореме синусов: x/sin(30)=14/sin(135), значит 
x= \frac{14}{ \sqrt{2} } = \frac{14 \sqrt{2} }{ \sqrt{2} \sqrt{2}} =
\frac{14 \sqrt{2}}{2} =7 \sqrt{2}" alt=" \frac{x}{ \frac{1}{2} } = \frac{14}{ \frac{ \sqrt{2} }{2} } =>
x= \frac{14}{ \sqrt{2} } = \frac{14 \sqrt{2} }{ \sqrt{2} \sqrt{2}} =
\frac{14 \sqrt{2}}{2} =7 \sqrt{2}" align="absmiddle" class="latex-formula">