The cereal box is a cuboid. we would find the volume of the original cereal box by applying the formula for determining the volume of a cuboid which is expressed as
Volume = length x width x height
From the information given,
height = 12
width = 3
length = 8
Volume of original box = 8 x 3 x 12 = 288
Since the cereal company wants to create a box with half the volume of this box,
Volume of the new box = 288/2 = 144
the dimension of the width of this box would be
3/2 = 1.5 inches