... 12b 2 102b252b22 16b 2 31 2b21 b252b21 b22 16b 2 31 0 5216b 2 31 0 1 16b 5216b 1 16b 2 31 16b 5 231 16b165 231 16b 52 31 165211516Choice (A) is your answer.21. A There’s no ... the lesser prime are 2, 3, or 5.Prime numbers starting in the 20s are 23, 29, 31 , and 37 . Use a littletrial and error, and you’ll realize that the difference between 23 and 2 is21. Those are ... 20001000 30 00 9000 27000In the 1980s, the population fell by one-half, so divide 27,000 by 2.Then go back to multiplying by 3. 1950 1960 1970 1980 1990 20001000 30 00 9000 27000 13, 500 40,500Your...