You may not have noticed that this is an equation, not an inequality. The solution to the given inequality is not one number, but an infinite set of numbers, which can be represented by an inequality. When dividing both sides of the inequality by $\displaystyle-{6}\usepackage{cmbright}\Huge\$ , the direction of the inequality sign changes. The correct answer is $\displaystyle{z}\ge-{9}\usepackage{cmbright}\Huge\$ .