Answer: 0.25
The starting rectangle (on the left) is larger than the ending rectangle (on the right). This means the scale factor is some value between 0 and 1, not including 0 or 1 itself.
To find the scale factor, we divide corresponding sides. We divide the vertical side 1.5 of the figure on the right over its corresponding pair on the left.
So,
scale factor = (new)/(old) = 1.5/6 = 0.25
Since 0.25 = 1/4, this means that the rectangle on the right is 1/4th as small compared to the one on the right.