Question 958687
x=2 times the width of deck
{{{(20m+x)(12m+x)=600m^2}}}
{{{x^2+32x+240=600m^2}}} Subtract 600m^2 from each side.
{{{x^2+32x-360=0}}}*[invoke quadratic "x", 1, 32, -360 ]
x=8.82 meters, width=0.5x=4.41 meters
ANSWER The width of the deck is 4.41 meters.