a. px is the pointer to x
*px dereferences this pointer, giving us 10 (= the value x)
(*px)++ is 10 + 1, which is 11
so x = 11, but since this is a post-fix operation, z is still 10
b. *py dereferences the pointer py, giving us 20 (= the value of y)
*py + y is 20 + 20, which is 40
so z = 40
c. x and y are integers, and an int cannot be dereferenced.