SQL Server 2012 setup might fails with below error when you do not have .Net frame work 3.5 features.

{
TITLE: Microsoft SQL Server 2012 Setup
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The following error has occurred:
Error while enabling Windows feature : NetFx3, Error Code : -2146498298 , Please try enabling Windows feature : NetFx3 from Windows management tools and then run setup again. For more information on how to enable Windows features , see http://go.microsoft.com/fwlink/?linkid=227143
For help, click: http://go.microsoft.com/fwlink?LinkID=20476&ProdName=Microsoft%20SQL%20Server&EvtSrc=setup.rll&EvtID=50000&ProdVer=11.0.2100.60&EvtType=0x681D636F%25401428%25401
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BUTTONS:
}

To resolve the above error open server manager à Add roles and features wizard à select .Net frame work 3.5 feature and install as shown in below image.

If the installation of.Net frame work 3.5 feature fails most probably it should be because of incorrect SXS folder. In such case choose an alternate SXS folder for installation in “confirm installation screen” (Which would appear as soon as you click install on above screen)
You will find SXS folder in Windows DVD under \sources\SXS