Mismatch between processor architectures

I'm completely new to the mobile application development world. When trying to run a test application I get this error twice:

  C: \ Windows \ Microsoft.NET \ Framework \ v4.0.30319 \ mscorlib.dll "," x86 ", and" .   This mismatch may cause runtime failures. Please consider changing the targeted processor architecture of your project through the Configuration Manager so as to align the processor architectures between your project and references, or take dependency on references with a processor architecture that matches the targeted processor architecture of your project. TestMobile.Core
   mismatch MSIL x86

I'm using VS2015, I have .NET 4.5 installed, windows 8 SDK tools, and MultilingualAppToolKit.

I checked the configuration manager and everything seems ok, platform target "Any CPU".