The SQL setup won’t start when you double click setup.exe, when executing setup.exe from command prompt you will receive the following error:
ERROR: Runtime error: This method explicitly uses CAS policy, which has been obsoleted by the .NET Framework. In order to enable CAS policy for compatibility reasons, please use the NetFx40_LegacySecurityPolicy configuration switch. Please see http://go.microsoft.com/fwlink/?LinkID=155570 for more information.
The solution is to remove .Net Framework 4.5
After removing you can install SQL.