Question 1008981
If b is uniform width of brick border, x and y are the patio dimensions, A is the total area of combined patio and border, then you have


{{{system(x=8,y=10,A=195,b=unknownBorderWidth)}}}


Patio area only, {{{xy}}}
total combined, {{{(x+2b)(y+2b)=A}}}


Solve for b in {{{highlight((x+2b)(y+2b)=A)}}}, and substitute the given values when you are ready.  (Maybe the resulting quadratic expression equal to zero is factorable and maybe not.)


{{{xy+2yb+2xb+4b^2-A=0}}}
{{{4b^2+(2x+2y)b+xy-A=0}}}----you could keep going purely in symbols, but this is where you might be comfortable in substituting the given values for x,y,A, before continuing.