Using the equation, 4fe + 3o2 2fe2o3, if 6 moles of iron (iii) oxide were produced, how many moles of iron would be required?

The answer is:  "Twelve (12) moles of Fe (iron) would be required."  

or:

The answer is:  "12" .

Note:  The balanced chemical equation is given:

    4 Fe  +  3 O₂  →  2 Fe₂O₃

The product is:  2 moles of  Fe₂O₃ ;  that is, "2 moles of iron (III) oxide" .

      →  If SIX (6) moles of iron oxide were produced, that would be "3 (three) times the number of moles of iron oxide produced (3 TIMES 2) ;
      → since:  "6 ÷ 2 = 3" ;  and since the equation is balanced.

           → So we want to find the number of moles of "iron (Fe)" needed in such a situation.  In the balanced chemical, we have "4 Fe" (that is, "FOUR (4) moles of iron") ; so we multiply that number by "3", proportionally:

                      →   4 (moles Fe) * (3) = 12 (moles Fe) .