Question 1200062
"Internal base area"?  Do we need to know the thickness of the carboard?


Just looking at base area, ignoring material thickness
{{{(15-2x)(18-2x)=130}}}
That's to start.
More than one way to go.


You might recognize the possibility to find two factors of 130 which differ by 3.  They would be 10 and 13.  Try using that.


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{{{(15-2x)(18-2x)=10*13=130}}}


{{{system(15-2x=10,18-2x=13)}}}

{{{5=2x}}}

{{{x=2&1/2}}}


VOLUME is  {{{(2.5)(10)(13)=youcomputethis}}}.