College Algebra, Chapter 2, Review Exercises, Section Review Exercises, Problem 54

Chris is hired by an accounting firm at a salary of $\$60,000$ per year. Three years later his annual salary has increased to $\$70,000$. Assume that his salary increases linearly.
a.) Find an equation that relates his annual salary $s$ and the number of years $t$ that he has worked for the firm.

$\begin{equation} \begin{aligned} s &= \left( \frac{70,500-60,000}{3} \right)t + 60,000\\ \\ s &= 3500 t + 60,000 \end{aligned} \end{equation}$


b.) What do the slope and the $s$-intercept of his salary equation represent?
The slope 3500 represents the annual increase of Chris salary and the $s$-intercept is the salary offered to Chris for the first year.

c.) What will his salary be after 12 years with the firm?

$\begin{equation} \begin{aligned} \text{when } t &= 12\\ \\ s &= 3500(12) + 60,000\\ \\ s &= 102,000 \end{aligned} \end{equation}$

After 12 years, Chris salary will be $\$102,000$