(2,3) = (a,b)
(6,6) = (c,d)
D-B/C-A (To help remember, Dog Bites Cat's Arm)
6-3/6-2 = 3/4
Flip it
4/3 - the answer is c
Okay so...
There are 21 groups of 3.
21 x 3 = 63.
63 people are in the room.
Answer: 
Step-by-step explanation:

Answer:
In 39 years time, the population doubled.