This document contains a group assignment for a number theory class. It lists the names of three students: Rizky Titie R, Shofia Hidayah, and Marlia Sari P. It then provides examples of math tricks for multiplying numbers by 11, 55, 77, 88, and 99. Each trick shows the steps to break down a number based on its digits and then recombine it to get the answer. It also includes an attempt to prove an equation involving zeros that results in an undefined solution.