#### Answer

$-8\sqrt{3}$

#### Work Step by Step

Using the properties of radicals, the expression, $
2\sqrt{3}-5\sqrt{12}
,$ simplifies to
\begin{array}{l}\require{cancel}
2\sqrt{3}-5\sqrt{4\cdot3}
\\\\=
2\sqrt{3}-5\sqrt{(2)^2\cdot3}
\\\\=
2\sqrt{3}-5\cdot2\sqrt{3}
\\\\=
2\sqrt{3}-10\sqrt{3}
\\\\=
-8\sqrt{3}
.\end{array}