###Human: Matias is a salesman in a bookstore. He sold 7 books on Tuesday and three times as many on Wednesday. If the sales from Wednesday were tripled on Thursday, how many books did Matias sell during these three days combined?, ### Assistant: Matias sold 7 * 3 = 21 books on Wednesday, as he sold three times more books than on Tuesday.
The sales from Wednesday were tripled on Thursday, which means Matias sold then 21 * 3 = 63 books.
That means in total Matias sold 7 + 21 + 63 = 91 books during these three days. 
 So the answer is :  91