Question 838925
there is no accompanying figure.
however, the postulates that reference lines are:




    Postulate 1: A line contains at least two points.

    Postulate 3: Through any two points, there is exactly one line.

    
the statement you want to explain using the postulate is:
Points R and Z are in line ZR.


i would guess that postulate 3 would be the one to explain it, although you could also use postulate 1, since the line ZR is defined as the line between the points Z and R.

postulate 3, however, is more to the point, since postulate 1 indicates there may be more points on the same line while postulate 3 indicates that there is only one line between 2 points, that line being the line labeled ZR.

i would go with postulate 3.


a good reference of postulates and theorems in geometry can be found at the following link:


<a href = "http://www.riverview.wednet.edu/parade/teachers/mcclintict/Geometry-1/Geo-PostulatesTheorems-List-2011.pdf" target = "_blank">http://www.riverview.wednet.edu/parade/teachers/mcclintict/Geometry-1/Geo-PostulatesTheorems-List-2011.pdf</a>


i think postulates and theorems relating to lines is on page 3.