Question

If y varies directly with x, and If y = -18 when x = 6, how do you find x when y = 6?

Answer 1

Another way of looking at this problem type

`x=-2`

Explanation:

Firstly, the solution provided already is correct in its approach and it has many applications.

Let us consider the use of the constant conversion factor of k

This is where the use of k comes from
Suppose we had for example `2/3-> k ~~ 0.666....`

Now compare that concept to:

`x/y=6/(-18)` if you divide this out you end up with k

What if we wrote it as:

`x/y=6/(-18) =x/6`

Then the solution is presented in the familiar form of ratio

Multiply both sides by 6 and you end up with:

`6xx6/(-18)=6xx x/6`

`(6xx6)/(-18)=6/6 x`

`x=-36/18 = -2`

Either of the approaches will work