A square with sides 6 units in length is reflected across the x -axis. How long are the sides in the reflected figure?

When a figure is reflected across the x-axis, the x-coordinate of each point is negated, while the y-coordinate remains the same.

Therefore, the x-coordinates of the original square are:
(0, 0), (6, 0), (6, 6), (0, 6)

After reflecting across the x-axis, the x-coordinates become:
(0, 0), (6, 0), (6, -6), (0, -6)

We can see that the y-coordinates remain unchanged.

So, the length of each side in the reflected figure is still 6 units.

Therefore, the sides in the reflected figure are 6 units in length.