1. **Problem:** If all of the deciduous trees were specified to be staked with 2 stakes each, how many stakes would be necessary? 2. **Formula:** Number of stakes = Number of deciduous trees \times Stakes per tree 3. **Step:** Count the deciduous trees from the plan. According to the description, there are 9 deciduous trees. 4. **Calculation:** $$\text{Number of stakes} = 9 \times 2 = 18$$ 5. **Answer:** 18 stakes are necessary.