In a large stock pot, brown the ground beef over medium heat. Drain any excess fat away. Return the met to the pot and add the onions. Cook for about 3 minutes. Add the garlic and cook, stirring constantly for about a minute. Add the beef broth and chopped potatoes. Bring to a boil. Cook for about 5 minutes, then add the tomato sauce, tomatoes (undrained), and frozen mixed vegetables. Return to a boil ,then reduce the heat to a simmer and cover. Cook until the potatoes and vegetables are tender. Add salt and pepper to taste. Then stir in a tablespoon of white vinegar.