On the number line shown above, the tick marks are equally..

[swerve]

On the number line shown above, the tick marks are equally spaced. Which of the following statements about the numbers x, y, and z must be true?

I. xyz < 0
II. x + z = y
III. z(y - x) > 0

A. I only
B. II only
C. III only
D. I and III only
E. I, II and III.

The OA is E.

Please, can any expert explain this PS question for me? I tried to solve it but I don't understand what's the symbol mean? I need your help. Thanks.

[GMATWisdom]

On the number line shown above, the tick marks are equally spaced. Which of the following statements about the numbers x, y, and z must be true?

I. xyz < 0
II. x + z = y
III. z(y - x) > 0

A. I only
B. II only
C. III only
D. I and III only
E. I, II and III.

The OA is E.

Please, can any expert explain this PS question for me? I tried to solve it but I don't understand what's the symbol mean? I need your help. Thanks.

as they are equally spaced let that spacing be =1
then x= -1, y=+1, z=+2
I. xyz=-2 which is < 0
II. x + z= +1 which is equal to y
III. z(y-x) = 2(1+1)=4 which is >0
thus all 1,2 & 3 are true
hence option E