If you're targeting your projecto to .Net core 2.0 and it's a ASP.NET Core, than you should follow these instructions on microsoft docs. You don't need those references to System.Web.
You can do area registration with MapRoute in your startup class for example, and the folder/file structure will do the rest:
...
app.UseMvc(routes =>
{
routes.MapRoute(
name: "areaRoute",
template: "{area:exists}/{controller=Home}/{action=Index}/{id?}");
routes.MapRoute(
name: "default",
template: "{controller=Home}/{action=Index}/{id?}");
});