Question

If `y=6` when `x=9`, how do you find `x` when `y=12`?

Answer 1

`x=18`

Explanation:

Note: this is if there is no specified or necessary formula for `x` and `y`

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Proportions. Use `x/y` format.

First set: `9/6`
Second set: `x/12`

Set them equivalent to each other:

`9/6=x/12`
`9*12=x*6` apply cross multiplication equivalency
`108=6x` simplified
`108/6=x` divide to isolate x
`18=x`