1. **Stating the problem:** Solve the equation $x + 5 = 12$ using addition or subtraction. 2. To isolate $x$, subtract 5 from both sides: $$x + 5 - 5 = 12 - 5$$ which simplifies to: $$x = 7$$ 3. **Another example:** Solve $y - 3 = 10$. Add 3 to both sides to isolate $y$: $$y - 3 + 3 = 10 + 3$$ which gives: $$y = 13$$ 4. **Third example:** Solve $2 + z = 9$. Subtract 2 from both sides: $$2 + z - 2 = 9 - 2$$ resulting in: $$z = 7$$ These methods use addition or subtraction to isolate the variable by performing the same operation on both sides of the equation, maintaining equality and solving step-by-step.