I'm learning Photoshop from textbook lessons, as well as online tutorials I find through Google.

I am trying to crop away the wedges in this photo, using the lesson Crop, Straighten, and Size.



The lesson told me to check "Relative" in the dialogue box, so that the Width and Height boxes will tell me how many pixels will be cropped away, and then I'm supposed to double those numbers.

But when I follow the directions, the numbers turn to zero. Can anyone tell me what I'm doing wrong? Why did the instructions work on the textbook photo, but not on mine?

I tried to follow this online tutorial, but the Crop instructions don't make sense:

Straighten A Crooked Photo

I'm using Photoshop CS2. Will someone please help me?