Given Info: "The dashed triangle is the image of the solid triangle"
So the "before" is the large solid triangle and the "after" is the smaller dashed triangle.
The horizontal side of the solid triangle is 15 units. The corresponding side for the dashed triangle is 3 units. Dividing the two values gives: 3/15 = 1/5 = 0.2
Make this value negative. The reason why is due to the fact that we have a sort of reflection going on as we're scaling down the figure.
So the final answer is -0.2