#### Answer

$7$

#### Work Step by Step

Using $(a+b)(a-b)=a^2-b^2,$ or the product of the sum and difference of like terms, and the properties of radicals, the given expression, $
(\sqrt{12}+\sqrt{5})(\sqrt{12}-\sqrt{5})
,$ is equivalent to
\begin{array}{l}\require{cancel}
(\sqrt{12})^2-(\sqrt{5})^2
\\\\=
12-5
\\\\=
7
.\end{array}