1. The problem is to solve the equation or expression labeled as "oef 9" (exercise 9). Since the exact problem is not provided, please provide the full problem statement for accurate assistance. 2. Generally, to solve algebraic problems, we use formulas and rules such as combining like terms, applying distributive property, isolating variables, and simplifying expressions. 3. Please provide the full text or equation of "oef 9" so I can show step-by-step solution with formulas and explanations. Without the exact problem, I cannot proceed further.