Bob, a marathon runner, is preparing for a race.  He runs a total of 70 miles in the 3 days leading up to the race. On day one he runs 20 percent of the total miles and on day 2 he runs 50 percent of the remaining miles.  How many miles does he run on day three to complete the 70 miles?
Please reason step by step, and put your final answer within \boxed{}.
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