Question

if the dotted figure is the image, the original figure was reflected over the... x - axis y - axis

Explanation:

Step1: Recall reflection rule over y - axis

When a point $(x,y)$ is reflected over the y - axis, the new point is $(-x,y)$. For a figure, all its vertices follow this rule.

Step2: Analyze the figure

By observing the position of the original figure (solid - lined) and the reflected figure (dotted - lined), we can see that the x - coordinates of the corresponding vertices of the two figures have opposite signs while the y - coordinates remain the same. This is the characteristic of reflection over the y - axis.

Answer:

y - axis