Only the amount of gas is held constant.
Are there any choices to your question? If so what are they? Then I can answer. :)
Answer:
12.0108408
Explanation:
Denote the element with a letter like say X. Since it has a subscript of 5, then, X5.
Molecular mass=102.133g/mol.
% of X in compound =58.8/100
=0.588
Mass of X in the compound = 0.588*102.133 ( the % of X in compound * molar mass of compound)
= 60.054204
X5=60.054204
Then element X has a mass of 60.054204/5=12.0108408
