Answer
$37$
Work Step by Step
Multiply each term of the first complex number by each term of the second, then combine like terms and use the fact that $i^2=-1$to obtain:
$$
(-6+i)(-6-i)=-6(-6-i)+i(-6-i)
\\=-6(-6)-(-6)(i)+i(-6)-i(i)
\\=36+6i-6i-i^2
\\=36-(-1)
\\=36+1
\\=37
$$