Hey there!
C₅H₅ + Fe → Fe(C₅H₅)₂
Put a coefficient of 2 in front of C₅H₅ on the left side because there is a subscript of 2 after C₅H₅ in parenthesis on the right.
2C₅H₅ + Fe → Fe(C₅H₅)₂
Fe (iron) is already balanced since there is one on each side, so we don't need to change anything for that.
This is a synthesis reaction because two reactants, C₅H₅ and Fe, are yielding a single product, Fe(C₅H₅)₂.
Hope this helps!
