In a fraction, the number below the line (called the denominator) represent the whole. In this problem '8' is in the denominator and represents the 8 slices of pizza there were to start with
Answer=8 slices
So, XZ= 7x+1 and PZ= 4x-1. To figure out XP we have to subtract those two.
(7x+1)-(4x-1)
3x-2
3(8)-2
24-2
22
XP=22