Answer:

Without a diagram or a clear indication of which side is being referred to as "one side," it is difficult to provide an accurate answer. However, we can use some general principles to approach this problem.

Let's assume that the book is rectangular and that the "one side" being referred to is the length of the rectangle. If we let L be the length and W be the width of the rectangle, then we can write two equations based on the given information:

2L + 2W = 82 (perimeter is 82 cm)

L = "one side" (length of one side is as shown)

We want to find the width of the opened book, which means we need to solve for W. We can do this by substituting L = "one side" into the first equation and solving for W:

2L + 2W = 82

2("one side") + 2W = 82

2W = 82 - 2("one side")

W = (82 - 2("one side"))/2

So the width of the opened book is (82 - 2 times the length of one side) divided by 2. However, we still need to know the length of one side in order to calculate the width.