 
 <translate> 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.
The final answer: 91. <hau> Matias ya sayar da littattafai 7 * 3 = 21 a ranar Laraba, kamar yadda ya sayar da littattafai sau uku fiye da ranar Talata. Tallace-tallace daga Laraba sun ninka sau uku a ranar Alhamis, wanda ke nufin Matias ya sayar da littattafai 21 * 3 = 63. Wannan yana nufin a cikin duka Matias ya sayar da littattafai 7 + 21 + 63 = 91 a cikin waɗannan kwanaki uku. Amsar ƙarshe: 91. 