Question 898084
The only sense I can make here is that the quilt made covers 3 feet by 4 feet, leaving a path around the quilt on the piece of material unquilted.


x and y, the dimensions of quilted part
w, the width around the quilted part
expect x=3 and y=4.


Total Material Area, {{{(x+2w)(y+2w)}}}
Quilted Area, {{{xy}}}
Unquilted Area, {{{(x+2w)(y+2w)-xy}}}
The unquilted area is given as 18 square feet to be used for decorative border.


Meaning is {{{(x+2w)(y+2w)-xy=18}}}.
{{{xy+2yw+2xw+4w^2-xy=18}}}
{{{2yw+2xw+4w^2=18}}}
{{{4w^2+2w(x+y)=18}}}
{{{2w^2+w(x+y)=9}}}
{{{2w^2+w(x+y)-9=0}}}
Substitute the given or expected values x and y,
{{{highlight_green(2w^2+7w-9=0)}}}
{{{(2w+9)(w-1)=0}}}
Choose the factor which has a meaningful solution.
{{{highlight(w=1)}}}.


Border will be a uniform ONE FOOT Width.