In order to find the average increase in the price, we need to divide the difference in the price by the difference of time.
The price changed from $7.37 to 7.80, and the time changed from 2008 to 2009, so we have:
[tex]\text{average increase}=\frac{7.80-7.37}{2009-2008}=\frac{0.43}{1}=0.43[/tex]So the average increase in the price was $0.43.