Question

Given a set `{-3,2,-1,x}`, for what x would the mean of the set be -5?

Answer 1

`x=-18`

Explanation:

`mean=(Sigmax_i)/n`

or, "the sum of all the elements divided by the number of elements"(as we're talking about a set here.)

We already know the mean is `-5`, and there are 4 elements: `-3, 2, -1`, and `x`.

So adding together all our elements and dividing by how many there are, should give us a mean of `-5`. We will therefore end up with an equation which we can solve for `x`.

`-5=(-3+2-1+x)/4`

so
`x-2=-20`

`x=-18`