1. **State the problem:** An investor has stocks in two companies, A and B. Last year, Company A's stock was worth 4230 and Company B's stock was worth 3130. Company A's stock increased by 10% and Company B's stock increased by 20%. We need to find the total percentage increase in the investor's combined stock value. 2. **Write down the formula for percentage increase:** The percentage increase is given by $$\text{Percentage Increase} = \frac{\text{New Value} - \text{Original Value}}{\text{Original Value}} \times 100$$ 3. **Calculate the new values of each stock:** - Company A new value: $$4230 + 0.10 \times 4230 = 4230 + 423 = 4653$$ - Company B new value: $$3130 + 0.20 \times 3130 = 3130 + 626 = 3756$$ 4. **Calculate the total original and new values:** - Total original value: $$4230 + 3130 = 7360$$ - Total new value: $$4653 + 3756 = 8409$$ 5. **Calculate the total percentage increase:** $$\frac{8409 - 7360}{7360} \times 100 = \frac{1049}{7360} \times 100$$ 6. **Simplify the fraction:** $$\frac{\cancel{1049}}{\cancel{7360}} \times 100 \approx 0.1425 \times 100 = 14.25\%$$ 7. **Round to the nearest tenth:** $$14.3\%$$ **Final answer:** The total percentage increase in the investor's stock account is **14.3%**.