Aka absolute value hope that is what you needed
520 pages. 390 divided by 3 is 130. Take that times 4 and you get 520. To check it, I took 520 divided by four (or you can multiply by 1/4) and got 130. Hope it helps!
To find the circumference of a round object, you will take the diameter and multiply is by pi to get 78.5mm
-x-8y+5
Hope this helps, we have same name btw