There are nine elements in a 3x3 matrix: three on the main diagonal, and three pairs of off-diagonal elements. The condition says that the two elements in each off-diagonal pair are equal. If seven of the elements are 1 then only two elements are 0. There are two ways in which that can happen.Eitherthe two elements in one of the off-diagonal pairs are both 0,ortwo of the elements on the diagonal are 0. Count the number of ways in which each of these possibilities can occur.