In A Resealable Plastic Bag, Mix The Flour, Salt, And Pepper. Place The Liver Slices Into The Bag One At A Time, Seal, And Toss To Coat. In A Bowl, Mix The Water, Ketchup, Brown Sugar, Vinegar, Worcestershire Sauce, And Garlic Powder. Heat The Oil In A Skillet Over Medium Heat. Brown The Liver Slices On Both Sides. Pour The Sauce Mixture Over The Liver. Bring To A Boil, Reduce Heat, And Simmer 20 Minutes, Until Liver Is Tender.