Question 871846
Let w be the width of the frame around the picture.


Picture+Frame=1800, the entire area.  may be more straightforward.
{{{(20+2w)(30+2w)=1800}}}.
{{{2*2(10+w)(15+w)=18*10*10}}}
{{{(10+w)(15+w)=18*5*5}}}
{{{150+15w+10w+w^2=450}}}
{{{w^2+25w=450-150}}}
{{{w^2+25w-300=0}}}------you can finish this quadratic equation from here; just pick the value which works.