A book has w chapters. The first chapter is w5 pages long the second chapter is y pages long and the third chapter is w pages long. How many more pages does the second chapter have than the third chapter?
Let's denote the number of pages in the first chapter as x, the number of pages in the second chapter as y, and the number of pages in the third chapter as z. 

According to the conditions of the problem, we have the following system of equations:

x=w5

y=x+z

z=w

We need to find y-z. 

y-z=x+z-z=x=w5. 

Therefore, y-z=w5.