Let's start with a quick review of mean: to find the mean of a set of data, add the numbers in the data set together, then divide by the number of data points. For example, the mean of the data set 5, 6, 7, 8 is 5 + 6+ 7 + 8 / 4, or 6.5.
Now on to your question. To find the answer, first you'll need to figure out the sum of everyone's ages. You can do that using the following equation:
x / 6 = 6
In this equation, x stands for the sum of Tom's age and the ages of his brothers and sisters, and we're dividing x by 6 because there are 6 kids total (Tom plus 5 brothers and sisters). To find the value of x, multiply both sides by 6.
x / 6 = 6
x = 36
The sum of everyone's ages is 36. We'll need that number to figure out what the mean age will be ten years from now. In ten years, each kid will be ten years older. That equates to 60 additional years (10 years per person x 6 people). To find out what the mean age will be in ten years, add 60 years to x and divide by 6.
36 + 60 / 6 = y
96/6 = y
16 = y
In the above equation, y equals the mean age. After simplifying the equation, we find that in 10 years the mean age will be 16. Whew!