Write a complex percentage problem and outline the procedures for teaching students how to solve this type of problem.

Example Problem:
A store is having a sale with 25% off all items. If the original price of a jacket is $120 and a customer has a coupon for an additional 10% off the sale price, what is the final price the customer pays for the jacket?

Procedures for Teaching:

1. **Understanding the Problem:**
- Read the problem carefully.
- Identify the original price, the percentage of the sale discount, and the additional discount.

2. **Calculate the Sale Price:**
- Calculate the sale discount: Multiply the original price by 25% (0.25).
- Subtract the discount from the original price to find the sale price.

\[
\text{Sale Price} = \text{Original Price} - (\text{Original Price} \times 0.25)
\]

3. **Apply the Additional Discount:**
- Calculate the additional discount on the sale price: Multiply the sale price by 10% (0.10).
- Subtract the additional discount from the sale price to find the final price.

\[
\text{Final Price} = \text{Sale Price} - (\text{Sale Price} \times 0.10)
\]

4. **Verification:**
- Double-check the calculations.
- Ensure the final price makes sense in the context of the problem.

5. **Discussion:**
- Discuss the importance of understanding each step.
- Highlight common mistakes and how to avoid them.