I think you forgot to add the picture. However, any x = 4 equation will result in a graph with a vertical line on the x-axis. For example x = 20 will be a vertical line on x-axis 20.
Or, in a more difficult equation like this...
10x - 60 = 10
10x = 10 +60
10x = 70
x = 7,
where the graph looks like a vertical line with a point on the x axis on 7.
