9x-(3x-3)=21 Solve the equation. Select the correct choice below and if necessary, fill in the answer box to complete your choice. The solution set is (Simplify your answer. Type an integer or a fraction. Use a comma to separate answers as needed.) The solution is all real numbers. The solution is the empty set.

Which statements are true? check all that apply. the line x = 0 is perpendicular to the line y = –3. all lines that are parallel to the y-axis are vertical lines. all lines that are perpendicular to the x-axis have a slope of 0. the equation of the line parallel to the x-axis that passes through the point (2, –6) is x = 2. the equation of the line perpendicular to the y-axis that passes through the point (–5, 1) is y = 1.