I'll give the yearly increase (5107.5) I'll also throw in the amount of money after a year 25,537.5.
Step-by-step explanation:
20,430 *1.25 (the decimal form of 12.5 percent) is your increase per year is 5107.5 of which is 12.5 percent of 20,430. Once you multiply by your percent you subtract the beginning value by your answer. This is because she would not be gaining more than twenty thousand dollars per year, that's just silly.
This is true, because there is an infinite amount of real numbers in both, and they are both countably infinite (so these infinities are equal). Hope this helps!