Question

if the mean of the observations x,x+3,x+5,x+7,x+10 is 9,then find the value of x.

Answer 1

X = 4
5x + 25 \ 5 = 9
5x + 25 = 45
5x = 20
X = 4

Answer 2

mean = sum of all observations / total no. of observations
       9 = x+x+3+x+5+x+7+x+10 /  5
     45 = 5x + 25
     5x = 20
       x = 20/5
       x = 4

hope it helps !!!