`
(x * 12) + (x * 11) + (x * 10) + (x * 9) + (x * 8) + (x * 7) + (x * 6) + (x * 5) + (x * 4) + (x * 3) + (x * 2) + (x * 1) = 450
`

I need a formala to find x.

`x * 78 = 450`

`450 / 78 = x`

Found it!.