We are asked to determine the length of a picture that is originally 10 inches wide and 12 inches long.
By reducing it we must keep the same proportion between length and width. Therefore, the ratio between length and width must remain the same. The ratio between width and length is:
[tex]\frac{10}{12}[/tex]
Now, we set this equal to the ratio of the reduced picture:
[tex]\frac{10}{12}=\frac{9}{x}[/tex]
Therefore, the right proportion is B
