Hey there!
To find mean, median, and mode, I first suggest that you arrange the number set of any problem like this into smallest to largest, like so:
1, 4, 4, 4, 4, 5, 7, 8, 15, 15, 15
To find mean, or average, you need to take all of these numbers, add them up, then divide that sum by the amount of numbers there are (in this case, 11):
1 + 4 + 4 + 4 + 4 + 5 + 7 + 8 + 15 + 15 + 15 = 82
82 / 11 = 7.45, your mean
To find median, you need to find the number in the exact middle of the number set when they're going from smallest to largest. For future reference, if you have an even amount of numbers, you'll have two middle numbers; just average these out using the steps above.
1, 4, 4, 4, 4, 5, 7, 8, 15, 15, 15
The middle number is bolded, this is your median.
Finally, for mode, it'll be the number that repeats the most in your set. In this particular set, 4 repeats the most, so 4 will be your mode.
Hope this helped you out! :-)
