Answer:

To find x, we can use the formula for the mean (also known as the average) of a set of numbers:

mean = (sum of the numbers) / (number of the numbers)

We are given that the mean of 3, 8, 15, x, and 14 is 12, so we can write:

12 = (3 + 8 + 15 + x + 14) / 5

Multiplying both sides by 5:

60 = 3 + 8 + 15 + x + 14

Simplifying the right side:

60 = 40 + x

Subtracting 40 from both sides:

20 = x

Therefore, the value of x is 20.