As I said before, work it out on paper, you have a few ways to do it. One is messier to code but easier on the eyes, the other a bit more maths but easier to code.
Either way, its a logic issue not a coding issue, so have a go at working out how you might do it.
If nothing else, start a new console based app, and get it to print numbers 1-15 for page 1, and then move to page 2, and back, and so on. so you can concentrate purely on that aspect.