Salary calculation: solving proportional increase of two variables I would like to understand, proportionally, how much of someone's new salary is attributed to an increase in both their number of hours worked, and increased dolar wage respectively. Both these variables changed simultaneously, now I'd like to know how much each affects their new salary. For example: An employee's old wage was 20 hrs x \$10 = \$200. Their new wage is 25 hrs x \$15 = \$375. I want to know how many \$ of their new wage can be attributed to the increase in hours and how much is due to increase in wage. I'm finding it's not as simple as knowing that hours increased 25% and rate increased 50%, since that increased rate compounds total hours worked. Any direction to point me down is much appreciated.

He is being paid \$100 more for the 20 hours he was already working (at a 50% salary increase), and \$75 for the extra five hours (at the new rate).

You _could_ say that \$100 out of the \$175 total increase are entirely due to the increase in salary (that would be 4/7ths, or about 57.14% of the increase), and \$75 out of \$175 are entirely due to the new hours (3/7ths, or about 42.86% of the increase).

I'm not sure that would be entirely clear to someone listening to you saying that, though.