1. The problem is to solve a 9th grade math problem, but since no specific problem was given, let's consider a common example: solving a linear equation such as $2x + 3 = 11$. 2. The formula or rule used here is to isolate the variable $x$ by performing inverse operations. 3. Start by subtracting 3 from both sides: $$2x + 3 - 3 = 11 - 3$$ which simplifies to $$2x = 8$$ 4. Next, divide both sides by 2 to solve for $x$: $$\frac{\cancel{2}x}{\cancel{2}} = \frac{8}{2}$$ which simplifies to $$x = 4$$ 5. Therefore, the solution to the equation $2x + 3 = 11$ is $x = 4$. This method applies to many linear equations: perform inverse operations step-by-step to isolate the variable.