Units used to describe volume are cubic
The formula to find the area of a triangle is

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The cosine of 30° is √3 / 2.
Since cosine is Adjacent over Hypotenuse, Hypotenuse = (2 / √3) * 9 = 18 / √3.
The cosine of 45° is √2 / 2.
Therefore, X = (2 / √2) * (18 / √3) = 36 / √6 = 18 / √1.5 = C