The total cost of buying bread and ham was $50+$150 = $<<50+150=200>>200
Together with the cake, Tina paid $200+$200 = $<<200+200=400>>400 for the items
Since the total percentage for all the items is 100%, the cost of ham and bread is $200/$400 * 100% = <<200/400*100=50>>50% of the total cost of items.
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