$-2 \sqrt{3}+3 \sqrt{27}$

Step 1 ：Given the expression \(-2 \sqrt{3}+3 \sqrt{27}\)

Step 2 ：We simplify the square roots first. \(\sqrt{3}\) is already in its simplest form, but \(\sqrt{27}\) can be simplified to \(3\sqrt{3}\)

Step 3 ：So the expression becomes \(-2 \sqrt{3}+3 *(3\sqrt{3})\)

Step 4 ：Which simplifies to \(-2 \sqrt{3}+9 \sqrt{3}\)

Step 5 ：Finally, we combine like terms to get \(7 \sqrt{3}\)

Step 6 ：Final Answer: \(\boxed{7 \sqrt{3}}\)