Given the data:
X, 4, 9, 13, 2, 31, 3
Mean of data = 11
Let's find the value of X.
To find the mean of a data set, divide the sum of the values by the number of values in the set.
Apply the formula:

Where:
number of values = 7
mean = 11
sum of data = X + 4 + 9 + 13 + 2 + 31 + 3
Thus, we have:

Let's solve for x in the equation above.
Multiply both sides of the equation by 7 to eliminate the denominator:

Subtract 62 from both sides of the equation:

Therefore, the value of X is 15.
ANSWER:
15