Any line that has a zero slope is a horizontal line.
Any line with an undefined slope is a vertical line.
So if the line has undefined slope and passes through (3/2, 2/3)
At that point x = 3/2 = 1.5, and y = 2/3.
The graph would be a line that is vertical, and as such it would an equation:
x = 3/2. This is the vertical line.
x = 3/2
