Mrs. Fredrickson has 80 chickens where 1/4 are roosters and the rest are hens. Only three-fourths of those hens lay eggs. How many chickens does Mr. Fredrickson have that do not lay eggs? Think carefully first, then make a decision:
Mrs. Fredrickson has 80 x 1 / 4 = 20 roosters. So he has 80 - 20 = 60 hens. Only 60 x 3 / 4 = 45 of the hens lay eggs. Thus, 60 - 45 = 15 hens do not lay eggs. Therefore, Mr. Fredrickson has a total of 15 hens + 20 roosters = 35 chickens that do not lay eggs. So, the answer is 35.