This isn't homework, I am boggling my head over it though.
I got all sorts of answers, just not the answer my book demands.
For what value of $x$ the mean of the given observations $2x - 5, x + 3, 7 - x, 5-x$ and $x + 9$ with frequencies $2,3,4,6$ and $1$ respectively is $4$?
I seriously cant solve this, help would be MUCH appreciated. Note: Please don't use any advanced statistics formula, we are still on the basics. Sum of $f_ix_i$ over sum of $f_i$ is all I can use.