Five people make five bears in five days, so 1 individual makes five days 1 bear, 20 people make 20 bears in five days, and 20 people make 80 bears in 20 days (20 divided by 5=4 4*20=80).
Solution: From the meaning of the question: 1 people do it for five days 1 bear, then 20 people do it for 20 days: 20/1= 20,20/5 = 4,4 * 20 = 80.