-4.46cm
Step-by-step explanation:
The horizontal midpoint of the page is;
The horizontal midpoint of the image is given as;
For the image to be centered, these to midpoints must be on the same point in the axis.
If we take the leftmost edge of the paper to be point zero on the axis, then, the distance accommodated by the paper is 10.795cm. The distance that goes beyond this leftmost edge is computed as;
On the axis, this is on the negative side. Therefore, the horizontal position for the left edge of the image that Joelle should use to center the image is -4.46cm.