11) \( -2 \sqrt{12}-\sqrt{12} \)

To simplify \( -2 \sqrt{12} - \sqrt{12} \), first, note that both terms contain the same radical, \( \sqrt{12} \). You can combine them as follows: \[ -2\sqrt{12} - 1\sqrt{12} = (-2 - 1)\sqrt{12} = -3\sqrt{12}. \] Next, simplify \( \sqrt{12} \). Since \( 12 = 4 \times 3 \), we have \( \sqrt{12} = \sqrt{4 \times 3} = 2\sqrt{3} \). Substituting this back into the expression gives: \[ -3\sqrt{12} = -3(2\sqrt{3}) = -6\sqrt{3}. \] So, the final simplified form is \( -6\sqrt{3} \).