Final answer:
To forecast the demand for the fourth month using the three-month moving average method, add up the demand for the past three months and divide by 3.
Step-by-step explanation:
To forecast the demand for the fourth month using the three-month moving average method, we need to find the average of the demand for the past three months. The demand for the three months are 20, 22, and 25 units. To find the average, we add up the three numbers and divide by 3: (20 + 22 + 25) / 3 = 67 / 3 = 22.33 units. Therefore, the forecasted demand for the fourth month is 22.33 units.