Question 941014
The floor area is 24 sq ft 
Thus L x W = 24 sq ft
The length is 6 more then 3 times the width
L=3W+6  Substitute second equation in first for L
(3W+6) x W=24
{{{3w^2 + 6W=24}}} Divide through by 3
{{{(3W^2+6W)/3=24/3}}}
{{{W^2+2W=8}}} subtract 8 from each side
{{{W^2+2W-8=8-8}}}
{{{w^2+2W-8=0}}}
*[invoke quadratic "W", 1, 2, -8 ]
So W=2 or -4
For an actual measurement only the 2 makes sense
So W=2 feet L=3W+6=3(2)+6=6+6=12 feet
CHECK:
The area is 24 sq ft
A=L x W
24 sq ft=12 ft x 2 ft
24 sq ft=24 sq ft