1. The problem is to solve for $d$ in an equation involving $d$. Since the user did not provide a specific equation, let's assume a general linear equation: $ad + b = c$ where $a$, $b$, and $c$ are constants. 2. The formula to solve for $d$ is to isolate $d$ on one side of the equation. This is done by subtracting $b$ from both sides and then dividing both sides by $a$. 3. Step-by-step: $$ad + b = c$$ Subtract $b$ from both sides: $$ad + b - b = c - b$$ $$ad = c - b$$ Divide both sides by $a$: $$\frac{\cancel{a}d}{\cancel{a}} = \frac{c - b}{a}$$ $$d = \frac{c - b}{a}$$ 4. This means $d$ equals the difference between $c$ and $b$ divided by $a$. 5. This method works for any linear equation where $a \neq 0$. Final answer: $$d = \frac{c - b}{a}$$