Answer:
4x^3-60x^2+216x
Step-by-step explanation:
Length of the tray = length of cardboard - 2 (side of the square ): 18-2x
Width of the tray = width of cardboard - 2( side of square); 12-2x
height of tray = sides of square: x
Volume of tray: x(18-2x)(12-2x) or 4x^3-60x^2+216x