Atom composition (simple question but hard for me)

[asz304]

1. The problem statement, all variables and given/known data

Fe3(Co)x, Fe is 33.26% by mass. Find the value of x.

3. The attempt at a solution

167.5425 g / 0.3326 = x ( 58.9326 g) / 0.6628

x = 5.6...

but the right answer given was x=12.

question #30:http://www.chem.mun.ca/courseinfo/c1050/Louise_Dawe/Basic%20Chemical%20Concepts%20I.pdf

Thanks

[Borek]

Co or CO?

[asz304]

Co, cobalt.