Answer:
13.5
Explanation
The two lengths for the first parallelogram is a ratio of 2:3
4 is 2 and 6 is 3
So for the other parallelogram, 9 would be in the first part of the ratio.
Meaning that the length BC would be 1/3 more than 9.
If we split 9 in half, it would be 4.5
9 + 4.5 = 13.5
hope this helps :)