1. **State the problem:** Solve the equation $3y - y = 12$ for $y$. 2. **Use the formula and rules:** Combine like terms on the left side. The rule is to add or subtract coefficients of the same variable. 3. Combine like terms: $$3y - y = (3 - 1)y = 2y$$ So the equation becomes: $$2y = 12$$ 4. **Isolate $y$:** Divide both sides by 2 to solve for $y$. Show the cancellation step: $$\frac{\cancel{2}y}{\cancel{2}} = \frac{12}{2}$$ 5. Simplify: $$y = 6$$ **Final answer:** $y = 6$