Final answer:
To calculate the average lateness using the FCFS rule, add up the lateness values and divide by the total number of values.
Step-by-step explanation:
To calculate the average lateness using the FCFS (First-Come, First-Served) rule, we need to find the mean of the lateness values. In this case, the lateness values are 13.5, 12, and 12.
Step 1: Add up all the lateness values: 13.5 + 12 + 12 = 37.5
Step 2: Divide the sum by the total number of values: 37.5 ÷ 3 = 12.5
Therefore, the average lateness using the FCFS rule for the given jobs is 12.5 minutes.