1. You have 13 units to study in 3 days. 2. To find out how many units you need to study per day, divide the total units by the number of days. 3. Calculate: $$\frac{13}{3} = 4.333...$$ 4. This means you need to study approximately 4 to 5 units each day to cover all 13 units in 3 days. 5. Plan your study schedule accordingly, focusing on 4 units on two days and 5 units on one day, or distribute as per your convenience.