math
posted by bob .
suppose your salary was 28,500 in 2010 and 32,000 in 2016. Assume your salary follows a linear growth pattern.

How much are you making in 2013?
Since 2013 is half way between 2010 and 2016, in 2013, the salary is (28500+32000)/2 = 30250.
You can also use the point of division formula.