Question 1067205

Side of square a = w
Length of rectangle {{{l=w+10}}}
Area of square {{{A = a^2 = w^2}}}
Area of rectangle {{{R = l*w = (w+10)*w}}}
Sum of A+R=208 so
{{{w^2+(w+10)*w=208}}}
{{{w^2+w^2+10w-208=0}}}
{{{2w^2+10w-208=0}}}
{{{w^2+5w-104=0}}}
{{{w=(-5+-sqrt(5^2-4*1*104))/(2*1)}}}
The equation has two roots, w=8 and w=-13. Obviously we keep only the positive.
So the side of the square is 8m.