1. **Problem Statement:** Calculate the percentage increase when a quantity changes from 120 to 150. 2. **Formula:** Percentage Increase = $$\frac{\text{New Value} - \text{Original Value}}{\text{Original Value}} \times 100$$ 3. **Explanation:** To find the percentage increase, subtract the original value from the new value to find the increase amount. Then divide this increase by the original value to find the fraction of increase relative to the original. Finally, multiply by 100 to convert this fraction to a percentage. 4. **Calculation:** $$\text{Increase} = 150 - 120 = 30$$ $$\text{Percentage Increase} = \frac{30}{120} \times 100 = 0.25 \times 100 = 25\%$$ 5. **Answer:** The percentage increase from 120 to 150 is 25%.