My book says that I need to give another name for /_A , What does that mean?
The notation "/_A" is typically used in mathematics or computer science to represent a placeholder for a concept, value, or variable. When your book asks you to give another name for "/_A," it means you need to come up with a different name or symbol to represent the same idea as "/_A."
To give another name for "/_A," you can choose any letter or symbol and assign it to represent the same concept. For example, you could use "/_B," "/_X," or even a Greek letter like "/_α" to indicate the same thing as "/_A" in the context of your book. The important thing is to ensure that the new name you select is clear and unambiguous, so that it doesn't cause confusion in the context of the problem or topic you are working on.