Milly is selling Girl Scout cookies. she sale 8 boxes of cookies every 3 days. How many days will she sales in 56 days
To find out how many sets of 3 days are there in 56 days, we divide 56 by 3.
56 / 3 = <<56/3=18.6>>18.6
Since Milly can only sell in whole sets of 3 days, she can sell for a maximum of 18 sets of 3 days.
Therefore, Milly can sell a total of 18 * 8 = <<18*8=144>>144 boxes of cookies in 56 days. Answer: \boxed{144}.