The document contains 9 systems of linear equations with 9 unknown variables each (x1, x2, ..., x9). Each system has 9 equations in the form of Ax = b, where A is a 9x9 coefficient matrix, x is a 9x1 variable vector, and b is a 9x1 constant vector. The coefficients and constants define the 9 linear equations for each system. There are a total of 7 systems fully defined, with the 8th system shown partially.