From the question provided;
represents the percentage change in beer 2007.
For the year 2007, x = 7.
Therefore, for the year 2009, the percentage change would be represented a follows;
For the year 2009, x = 9 represents the year 2009
ANSWER:
(a) The percentage change is a reduction by 6.8% (that is -6.8)
(b) x = 9 represents the year 2009