Question 1093951
x and y for original length and breadth;
A, the same area for original and new rectangles


{{{system(x=y+3,A=xy)}}}



New rectangle has dimensions x+9 and y-5 for length and breadth.
{{{A=(x+9)(y-5)}}}


Maybe you can do the algebra and arithmetic steps from here.  You could start buy substituting for x into both A equations, and then simplify them.