Question 1008345
This cement walkway is a three-dimensional rectangular frame.  Your 1 foot thickness is for the up-down direction, and you have unknown uniform width.  The question asks for this uniform width.


Analyze the description.
Let u be the uniform width of the pathway or walkway around the pool.
Inner area for the pool,  {{{25*10}}} square feet;
Outer area of the frame or walkway PLUS pool,  {{{(25+2u)(10+2u)}}};
The TOP  or the BOTTOM area for the walkway is  {{{(25+2u)(10+2u)-25*10}}};


Use the next two facts:
height or up&down thickness is 1 foot, and the volume for the walkway must be 304 cubic feet.


Walkway base area multiplied by 1 foot thickness is the 304 cubic foot of volume.
{{{highlight(((25+2u)(10+2u)-25*10)*1=304)}}}.
Simplify this, and once in a comfortable general quadratic equation form, solve for u.


I leave this solution to the extent shown, not finished and you just need to do those arithmetic or algebra steps.