Use Gauss-Jordan row reduction to solve the given system of equations. HINT [See Examples 1-6.] (If there is no solution, enter NO SOLUTION. If the system is dependent, express your answer in terms of x, where y = y(x) and z = z(x).) x + y − z = −6 x − y − 7z = −8 0.75x − 0.5y + 0.25z = 18 x + y + z = 4