what do points on the line parallel to the y-axis in 3 units to the left of it
have in common?with a summary.

Draw the line. Then mark some point arbitrarily and compare their coordinates
to see what they have in common.

 

I have marked some points arbitrarily on that line.  The top one is (-3,7), the
next one down is (-3,3), the bottom one is (-3,-8).  Notice that they all have
the same x-coodinate, namely -3.

That's the answer.  All the points on that line have in common the fact that
their x-coordinates are -3.  

Edwin
AnlytcPhil@aol.com