Find the area of the rectangle. You can find the area of a rectangle with the following formula:
![A = wl](https://img.qammunity.org/2019/formulas/mathematics/high-school/hd5gscjltyqa9t0y4ez9qejv0d5idsj665.png)
w = width, and l = length.
Plug in your width and length:
![20 * 10 = 200](https://img.qammunity.org/2019/formulas/mathematics/high-school/f6kzdx0tnknd15wn8f8sh84lllg1678c04.png)
The area of the rectangle is 200 square centimeters.
The area of a square is also given by width * length. Multiply the sides together:
![2x * 2x = 4x^(2)](https://img.qammunity.org/2019/formulas/mathematics/high-school/8o8kqrqjnhdk9oocaaylpj5tmcziznd6pb.png)
The area of a square is 4x^2.
Because you're cutting away the square from the rectangle, you will subtract the area of the square from the area of the rectangle. The following equation will be your answer:
![200 - 4x^(2) cm^(2)](https://img.qammunity.org/2019/formulas/mathematics/high-school/vbxvjs3iboglciq6h8pq08snn8qtz7u21x.png)