The mean of 5, 10, 15, and x is 12. What is the value of x?

The mean of 5, 10, 15, and x is 12. What is the value of x?

Step 1: Write down the numbers we have: 5, 10, 15, and x.
Step 2: Understand that the mean (average) is found by adding all the numbers together and then dividing by how many numbers there are.
Step 3: Since we have 4 numbers (5, 10, 15, and x), we will divide the total by 4.
Step 4: Set up the equation for the mean: (5 + 10 + 15 + x) / 4 = 12.
Step 5: Calculate the sum of the known numbers: 5 + 10 + 15 = 30.
Step 6: Substitute the sum back into the equation: (30 + x) / 4 = 12.
Step 7: To eliminate the division, multiply both sides of the equation by 4: 30 + x = 12 * 4.
Step 8: Calculate 12 * 4, which equals 48: 30 + x = 48.
Step 9: To find x, subtract 30 from both sides: x = 48 - 30.
Step 10: Calculate 48 - 30, which equals 18: x = 18.

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