Final answer:
To find out which version of .NET Core is installed, use the command 'dotnet --version' to see the active version, or 'dotnet --list-sdks' and 'dotnet --list-runtimes' to see all installed SDKs and runtimes, respectively.
Step-by-step explanation:
To tell what version of .NET Core is installed on your system, you can use the command line interface (CLI). Open a command prompt or terminal and execute the following command: dotnet --version. This will display the version of .NET Core that is currently active. If you have multiple versions installed and want to see all of them, use the command: dotnet --list-sdks for a list of SDKs (Software Development Kits) and dotnet --list-runtimes for a list of installed runtimes.
If you are on Windows, you can also check the installed versions by looking in the directory where .NET Core SDKs and runtimes are typically installed, which is generally under C:\Program Files\dotnet\.