Question 83317
Lets do this step-by step:

{{{3x^2y+2xy+5y}}}

substitute {{{x=3}}}-
this means we replace all x's with the number 3:

{{{3(3^2)y+2(3)y+5y}}}
which is the same as
{{{3(9)y+2(3)y+5y}}}
which simplifies to
{{{27y+6y+5y}}}

now replace the y terms with {{{y=2}}}
{{{27(2)+6(2)+5(2)}}}
which is the same as 
{{{54+12+10}}}
and
{{{54+12+10=76}}}

so the answer in its simplest form is 72

I hope this helps you.

Adam