mean (average) can be found by adding up all the numbers, then dividing by how many numbers there are.
mean : (12+15+16+17+18+20+22) / 7 = 120/7 = 17.14 <== notice that I put them in order...if u were just finding the mean, u wouldn't have to do that....but the median requires them to be put in order)
median (the middle number) = 17 mode (the number that appears most often) = there is none range (largest number - smallest number) : 20 - 12 = 8
next situation.. (0+0+0+1+2+2+2+3+3) / 9 = 13/9 = 1.44 ....mean median = 2 mode = 0 and 2 range = 3 - 0 = 3