Question 1002154
This works better if we can draw a picture or figure - not easy enough to do here.


Total piece of land area,  {{{40*32}}} square feet.


The rectangular slab, you only know that its placement in the middle of the piece of land must make a uniform width distance x between the boundary of the piece of land and a side of the slab.


The area which the slab covers is  {{{(40-2x)(32-2x)}}}.


Think about the two separate parts and the total.
Border area plus slab area is the piece of land area.
B for Border Area,
{{{B+(40-2x)(32-2x)=40*32}}}
{{{B=40*32-(40-2x)(32-2x)}}}


A brief re-read reminds us that "lawn" is for "border".  There is the lawn and the slab.


That is for beginning and analyzing.




(b) You want to find the y-intercepts?  What is (40-2x)(32-2x) when x is 0?   That will give the y-axis intercept.


(a)  There done earlier:  {{{(40-2x)(32-2x)}}}


(c)  If x=16  then what is the area of the slab?  Substitute into  the expression derived already.


For the rest, you should be able to think your way through.