Mrs. Fredrickson has 80 x 1/4 = <<80*1/4=20>>20 roosters.
So he has 80 - 20 = <<80-20=60>>60 hens.
Only 60 x 3/4 = <<60*3/4=45>>45 of the hens lay eggs.
Thus, 60 - 45 = <<60-45=15>>15 hens do not lay eggs.
Therefore, Mr. Fredrickson has a total of 15 hens + 20 roosters = <<15+20=35>>35 chickens that do not lay eggs.
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