You can learn how to use the prime factorization method to do this
GCF(12, 18, 40, 45) = 1
So I dont get what the problem is because there are no numbers for #2. So either I dont understand the problem or it is a trick question whereas the answer is UNDEFINED/IMPOSSIBLE.
Please see the attached image for a visual representation of our scale factor. We can set up this proportion by taking the DVD cover and poster values and placing them in fractions. Cross multiply and divide to solve for x.