1. **Problem Statement:** Calculate the new price of an item after a 15% increase in the first month, a 20% increase in the second month, and an 8% decrease in the third month, given the original price is 840. 2. **Formula and Rules:** - To increase a price by a percentage, multiply by $1 + \frac{\text{percentage}}{100}$. - To decrease a price by a percentage, multiply by $1 - \frac{\text{percentage}}{100}$. 3. **Step-by-step Calculation:** - Month 1 price: $840 \times 1.15 = 966$ - Month 2 price: $966 \times 1.20 = 1159.2$ - Month 3 price: $1159.2 \times 0.92 = 1066.464$ 4. **Final Answer:** The new price after three months is approximately $1066.46$.