Since each package weighed 4 pounds, the first butcher delivered 10 * 4 = <<10*4=40>>40 pounds
The second butcher's delivery was 7 * 4 = <<7*4=28>>28 pounds
The first two butchers therefore delivered 40 + 28 = <<40+28=68>>68 pounds
Subtracting that weight from the total weight of ground beef gives 100 - 68 = <<100-68=32>>32 pounds
It therefore means the third butcher delivered 32/4 = <<32/4=8>>8 packages.
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