Answer
$(x-5)(3x-4)$
Work Step by Step
The two numbers whose product is $ac=
3(20)=60
$ and whose sum is $b=
-19
$ are $\{
-15,-4
\}$. Using these two numbers to decompose the middle term, then the factored form of the given expression, $
3x^2-19x+20
$,is
\begin{array}{l}\require{cancel}
3x^2-15x-4x+20
\\\\=
(3x^2-15x)-(4x-20)
\\\\=
3x(x-5)-4(x-5)
\\\\=
(x-5)(3x-4)
.\end{array}
