The remaining shortest side of the right triangle is $-3\sqrt{3}$. However, since the length of a side cannot be negative, the correct positive value is $3\sqrt{3}$, which corresponds to option c.

Do you need more details or have any questions?

Here are five related questions to expand the topic:

1. How do you apply the Pythagorean theorem to solve for the sides of a right triangle?
2. What happens if both legs of the right triangle are equal?
3. Can the lengths of a triangle's sides ever be negative?
4. How does the Pythagorean theorem change in non-Euclidean geometry?
5. What other methods can you use to find missing sides in triangles besides the Pythagorean theorem?

Tip: Always check if the sides of the triangle you're calculating make sense in the context of the problem—lengths must be positive.