Given:
The polygon in the given figure are similar.
To find:
The missing side length.
Solution:
We know that the corresponding sides of similar figures are proportional.
The given polygons are similar, so the their corresponding sides are proportional.

So, the missing values in the equation of proportion are 15, 40, 32 respectively.
On solving the above equation, we get




Therefore, the value of x is 12.