We are asked to determine the rate of change of the values of vacation days between 2010 and 2011.
To do that we will use the following formula:
![r=(f(t_2)-f(t_1))/(t_2-t_1)](https://img.qammunity.org/2023/formulas/mathematics/college/ldhd7ku8vk3e8k8yfoh6638rmh0gz8emci.png)
Where:
![\begin{gathered} f(t_2),f(t_1)=\text{ vacation days for t2 and t1 respectively} \\ t_2,t_1=\text{ years in cosideration. } \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/5mhypbpnvkwqti3sncxbkvs47om0mwd097.png)
For the given case we have:
![\begin{gathered} t_2=2011 \\ t_1=2010 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/f9wvablp83cydn3yjvm1oddgmnud1va1ww.png)
The vacation days associated to each of the years are:
![\begin{gathered} f(2010)=16 \\ f(2011)=25 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/hzy2q53z84j9w3oexy97o2hop2vkps192g.png)
Now, we plug in the values in the formula for rate of change:
![r=(25-16)/(2011-2010)](https://img.qammunity.org/2023/formulas/mathematics/college/wo1fz4rq7h9lb8jydu9zbqv33hn6x7nm9j.png)
Now, we solve the operations:
![r=(9)/(1)=9](https://img.qammunity.org/2023/formulas/mathematics/college/hm88gua9s0fc3xw9g6vizn1q1g3cxeweey.png)
Therefore, the rate of change is 9 days per year.