Pre-image ABCD was dilated to produce image ​A′B′C′D′​ . What is the scale factor from the pre-image to the image?

Enter your answer in the box as a fraction in simplest form.

Two quadrilaterals labeled A B C D and A-prime, B-prime, C-prime, D-prime. Quadrilateral A B C D is larger than the other quadrilateral, which is to the right of quadrilateral A B C D. Side B C is labeled twelve, and side B-prime, C-prime is labeled nine.