Missing number

Example: 1, __ , 3, 4, 5; mean=3
Step 1: Let us call the missing number N.
Step 2: We know, Mean = (Sum of all numbers)/(Number of numbers);
Therefore, Sum of all numbers = Mean x Number of numbers
i.e., 1 + N + 3 + 4 + 5 = 3 x 5 = 15
Step 3: N + 13 = 15 (Add all numbers except the unknown N)
Step 4: N + 13 – 13 = 15 - 13 (Subtract 13 from both sides)
Step 5: N = 2 (The missing number)