Equating both: \[ \frac{9\sqrt{3}}{2} = \frac{1}{2} \times …

Equating both:
\[ \frac{9\sqrt{3}}{2} = \frac{1}{2} \times 6 \times h \]
\[ 9\sqrt{3} = 6h \]
\[ h = \frac{9\sqrt{3}}{6} \]
\[ h = \frac{3\sqrt{3}}{2} \]