Question 1192008
Try drawing the description and label as many parts as you can.


length of sheet,  2.7x
width of sheet, x
cutting out 3 inch square at each corner and fold up to make box;  the height of the box is 3 inches.


v for volum of the box
{{{highlight_green(v=3*(x-2*3)(2.7x-2*3))}}}

or 

{{{v=3(x-6)(2.7x-6)}}}
One obvious restriction is that x must be LARGER than 6.  


The values for v according to question #4 are 600 and 800.  So you x boundaries may be as
{{{600<=3(x-6)(2.7x-6)<=800}}}, which is two combined inequalities.  You can find the x values.  A graphing tool might help, or,...