We let his fixed monthly salary be x and
his fixed percentage be y so our equations will be:
[tex]2,550=x+15,000y ...(1)\\ 3,050=x+25,000y...(2) [/tex]
(2) - (1)
[tex]3,050-2,550=x+25,000y-(x+15,000y) \\ 500=10,000y \\ 0.05=y[/tex]
We substitute the value of y in the first equation:
[tex]2,550=x+15,000(0.05) \\ 2,550=x+750 \\ 1,800=x[/tex]