Find the X

I have a simple equation (that I've made even simpler here) that I can only solve it manually...
The equation is the following: "1/(1+1+1+X)" and I want the result to be "0,2". For this example, the X must be the number 2.

1/(1+1+1+2)=0,2

How I can do it automatically without having to manually choose the X value?

The result must always be 0,2, unless I want the end result to be 0,27 for example. But anyway I'll always have the final result, just need to find the X in each case.

Few more examples:
1/(1+1+2+X) = 0,23 X = 0,34783
1/(1+1+1,5+X) = 0,1818 X = 2

So, any tips besides returning to school?

A bit of algebraic manipulation will give us:

X = (1 - 3N) / N

where N is the number you quote above, like 0.2 and 0.23. If you use A2 to record that value, then you could have this formula in B2:

=(1-3*A2)/A2

Hope this helps.

Pete

Actually, you seem to have this:

1 / (1 + 1 + M + X) = N

so if you rearrange this you get:

X = (1 - 2N - MN) / N

where N could be cell A2 and M could be A3.

Hope this helps.

Pete

Thanks guys! This was exactly what I needed! Took me around 3 cells to make the equation... So more beautiful in just one cell.
Really appreciate it!