Question

Question was provided via image upload.

Explanation:

Step1: Assume the two parallelograms are similar.

For similar figures, the ratios of corresponding sides are equal.

Step2: Set up the proportion.

Let the unknown side be $x$. The proportion is $\frac{6}{12}=\frac{5}{x}$.

Step3: Cross - multiply.

We get $6x = 12\times5$.

Step4: Solve for $x$.

$6x=60$, so $x = 10$.

Answer:

10