Question: how to add reference to system.web.optimization for mvc-5?
Answer: Install the package from nuget: Install-Package Microsoft. ... 
Create and configure bundle(s) in App_Start\BundleConfig.cs: public class BundleConfig { public static void RegisterBundles(BundleCollection bundles) { bundles. ... 
Call the RegisterBundles() function from Application_Start() in your global.