Find the Additive Inverse: Determining the Opposite of 87

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

• Step 1: Identify the given number
• Step 2: Apply the definition of an opposite number
• Step 3: Conclude with the opposite number

Now, let's work through each step with detailed explanations:
Step 1: We are given the number $87$. This is a positive integer.
Step 2: The definition of an opposite number states that the opposite of any number $x$ is $-x$. Here, $x = 87$.
Step 3: Using the definition, the opposite number of $87$ is calculated as $-87$.

Therefore, the solution to the problem is $-87$.