I am struggling on how you get the $12.82. I did the step by step and I did get the $15.38, but now I am unsure how you get the $12.82.

2/(.20-.07)= 15.3846153846

15.3846153846 * 20% = 3.0769230769

15.3846153846 - 3.0769230769 = 12.3076923077