With 2 packages of sliced ham, Shane has 2 * 8 = <<2*8=16>>16 slices of ham.
Since he has 16 slices, Shane makes 16 sandwiches.
With 2 packages of sliced bread, he has 20 * 2 = <<20*2=40>>40 slices of bread.
To make the 16 sandwiches, he needs 16 * 2 = <<16*2=32>>32 slices of bread.
He has 40 - 32 = <<40-32=8>>8 slices of bread leftover.
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