Find the missing side of the top left triangle.

Let's analyze the top left triangle ABC, where angle B is 30 degrees, the hypotenuse AB is 18, and angle C is 90 degrees. We need to find the length of side AC, which is opposite to angle B. We can use the sine function to find the length of side AC: $$\sin(B) = \frac{AC}{AB}$$ $$\sin(30^{\circ}) = \frac{AC}{18}$$ We know that $$\sin(30^{\circ}) = \frac{1}{2}$$, so we can substitute this into the equation: $$\frac{1}{2} = \frac{AC}{18}$$ Now, we can solve for AC: $$AC = 18 \cdot \frac{1}{2}$$ $$AC = 9$$ Answer: 9