Question 1001411
{{{system(w=9,L=12,A=154,x=unknownUniformBorderWidth)}}}


Area border and flower bed, {{{(L+2x)(w+2x)}}}
Just area of bed, {{{wL}}}


The COMBINED area is A.
{{{highlight_green(highlight_green((L+2x)(w+2x)=A))}}}


Take this quadratic equation as far as you can in pure symbols before substituting the values to find or evaluate the uniform border width, x.