For 2a you take 486 and divide it by 162 and you’ll get three. 3 is the product of division so when you want to multiply you know the three needs to be a fraction.
2a = True
So now you know that when you take a # in that sequence and multiply it by 3 you get the # before it in the sequence.
So for 2b do 1 divided by 3 and keep on multiplying that # by 3 until 18 (the last and lowest # in the sequence) since it skips over 18 you know that 1/3 can’t be the starting point.
2b = False
So for 2c you take six and multiply it by 3 which is 18.
2c = True