The mean of 12, 15, 20, and x is 18. What is the value of x?*

Sure, here's how to solve it:

Step 1: Understand that the mean is calculated by adding all the numbers in a set and then dividing by the count of numbers.

Step 2: Set up the equation for the mean. In this case, it would be (12 + 15 + 20 + x) / 4 = 18.

Step 3: Simplify the equation. Add 12, 15, and 20 to get 47. So, the equation now is (47 + x) / 4 = 18.

Step 4: Solve for x. First, multiply both sides of the equation by 4 to get rid of the denominator on the left side. This gives you 47 + x = 72.

Step 5: Subtract 47 from both sides to solve for x. This gives you x = 72 - 47.

Step 6: Calculate the value of x. x = 25.