Calculate Parallelogram Area: Finding Height X with Base 20 and Side 11

To find the area of the parallelogram ABCD, we use the following information and process:

• Step 1: Recognize that $AB$, which equals 20 units, is the base of the parallelogram.
• Step 2: The height corresponding to this base is the line segment from $A$ perpendicular to $CD$, denoted $AE = x$.
• Step 3: Use the formula for the area of a parallelogram: $\text{Area} = \text{base} \times \text{height}$.

Given:

• Base $AB = 20$.
• Height $AE = x$.

$\text{Area} = AB \times AE = 20 \times x = 20x$

Therefore, the area of the parallelogram ABCD is $20x$.

The correct answer is $\boxed{20x}$.