По теореме синусов:
\(\frac{BC}{\sin A} = \frac{AC}{\sin B}\)
\(\frac{6\sqrt{2}}{\sin 45^\circ} = \frac{AC}{\sin 30^\circ}\)
\(\sin 45^\circ = \frac{\sqrt{2}}{2}\)
\(\sin 30^\circ = \frac{1}{2}\)
\(\frac{6\sqrt{2}}{\frac{\sqrt{2}}{2}} = \frac{AC}{\frac{1}{2}}\)
\(6\sqrt{2} \cdot \frac{2}{\sqrt{2}} = 2AC\)
\(12 = 2AC\)
\(AC = 6\)
Ответ: 6