Explanation:
We're dealing with a piece of cardboard 10" x 18". What shape is that? That's how we talk about rectangles. Length x Width. So we start with a rectangle of cardboard 18" long and 10" wide.
Now, what's with "open top box" - what does that mean? A box is a 3-dimensional rectangular solid. An open top means what? This is poorly-worded problem because we have to guess at "open top". It probably means "no lid". Can you picture or draw a box with no lid? You're going to need to do so to solve the problem.
You are being asked to find the volume of a box. What is the formula for the volume of a box?
That's right - Box Volume = Length x Width x Height = l x w x h = V
Which box? A box made out of a piece of cardboard by cutting a square out of each corner. Can you draw this?