Pagination error

I am getting this error(Call to undefined method App\Post::sortByDesc()).I am trying to sort items and then wanna use pagination. My code

    public function tutorials(Request $request)
    {

        $posts = Post::sortByDesc('visit_count')->paginate(5);

        $user = User::whereAdmin(1)->first();

        return view('blog',compact('posts','user'));
    }