we know that
1) Luis bought stock at ---------------> $66.80
2) The next day, the price increased $13.85--------> $66.80+$13.85=$80.65
3) This new price changed by −2 3 /4 % the following day
2 3/4%----> (2*4+3)/4----> 11/4 %----> 2.75%
so
(100%-2.75%)-----> 97.25%
the final stock price is $80.65*0.9725-----> $78.43
the answer is
$78.43
