Reduced row-echelon form and free variables

Move from Gaussian elimination to reduced row-echelon form and explicit solution families. This precalculus practice set covers unit pivots, clearing pivot columns, small RREF computations and parameter descriptions of underdetermined systems. Both single-select and multiselect questions challenge assumptions about free variables, contradictory rows and the uniqueness of reduced form. Worked explanations translate each matrix into equations and check entire families, using ordinary coordinate tuples rather than requiring abstract vector notation. Difficulty grows from form recognition to two-parameter solutions and equivalence reasoning.