To find the mean absolute deviation, (MAD) find the mean of the distances of each number from the mean.
For the first set:
MAD=\frac{|10.7-6.55|+|2.4-6.55|}2=\frac{4.15+4.15}2=\frac{8.3}2=4.15
For the second set:
MAD=\frac{|13.7-8.1|+|2.5-8.1|}2=\frac{5.6+5.6}2=\frac{11.2}2=5.6
Note that when you only have two data points the mean is directly between them, which is why the distances are the same.
Well if the price was $100 per couple and increased by 200% then it increased by 2 times the original price. So that means the price doubled so multiply. $100 by 2 which equals $200. So the current price is now $200.
