Question 1175511
.
<pre>

Let x be the dimension of the planted area (the square), in feet.


Then the garden, surrounded by the walkway of the uniform constant width is the square with the side length  (x + 2*3) = (x+6) feet.


Its area is 18000 square feet, which gives this equation


    (x+6)^2 = 18000.


Hence,   x+6 = {{{sqrt(18000)}}} = 134 feet (approximately),  and  x = 134 - 6 = 128 feet.     <U>ANSWER</U>
</pre>

Solved.