Answer
$6x^2+13xy-5y^2$
Work Step by Step
Using $(a+b)(c+d)=ab+ad+bc+bd$ or the FOIL Method, the product of the given expression, $
(3x-y)(2x+5y)
,$ is
\begin{array}{l}\require{cancel}
3x(2x)+3x(5y)-y(2x)-y(5y)
\\\\=
6x^2+15xy-2xy-5y^2
\\\\=
6x^2+13xy-5y^2
.\end{array}