Solve the Subtraction Equation: 20 - 20 = ?

To solve this problem, we'll follow these steps:

• Step 1: Identify the operation involved - subtraction.
• Step 2: Apply the operation by subtracting 20 from 20.

Now, let's work through these steps:

Step 1: Recognize that the operation is subtraction, specifically $20 - 20$.

Step 2: Perform the subtraction:
$20 - 20 = 0$

This follows the basic arithmetic rule that any number minus itself equals zero.

Therefore, the solution to this problem is $0$. The correct answer choice is Choice 2.