我的Jcombobox似乎正在工作，但当我在其中进行任何选择时，该程序似乎没有注册更改

Im working on a tax program for a CS class. I'm using neatbeans and programming in java. Im new to programming. My code appears to be working, however when I make a selection other than "single' from my JComboBox, the math doesn't change the way it should. It continues to use the math from the 'single' selection. Im wondering how to fix this problem. Also, there is a random 2000 dollars that seem to float in the math, so something is wrong with my calculation, but for the life of me, I can't figure out what. When the user inputs a lower 'taxable income' the math was always 2000 dollars above what it should be, so I subtracted 2000 to make it work. However, when the user inputs a large amount of 'taxable income' the math is always spot on, making my subtraction of 2000 dollars wrong. If anyone could take a glance at my code and help me out I would appreciate it. PS, only 'single' and 'married filing jointly' are filled in because I was trying to debug the program. Im working on a tax program for a CS class. I'm