Finding the percentage of alloy by mass( Max points)

a 32.4 g sample of an alloy of Mg and Al produces 1.66mol of H2 gas when added with HCl, what percentage of the alloy, by mass, is Mg??

The equations for the reactions are:

Mg + 2 HCl --> MgCl2 + H2
2Al + 6HCl --> 2AlCl3 + 3 H2.

if we let X = the mass of Mg, then (32.4 -X) = the mass of Al

use molar mass & the equation Mg + 2 HCl --> MgCl2 + H2
to convert the mass of Mg into moles of H2
(X) g Mg ( 1 mol H2 produced) / (24.3 grams Mg per mol) =
0.04115 X mol of H2 from Mg


use molar mass & the equation 1 mol 2Al + 3HCl --> 1AlCl3 + 1.5 H2.
to convert the mass of Al into moles of H2
(32.4 -X)g Al ( 1.5 mol H2 produced) / (26.98 grams Al per mol) =
(32.4 -X)g Al (0.0556) mol of H2 from Al


combine those two sets of moles & set them equal to the total mol of H2
0.04115 X & (32.4 -X) (0.0556) = 1.66 mol H2

0.04115 X & 1.80 - 0.0556 X = 1.66 mol H2

0.04115 X - 0.0556 X = 1.66 - 1.80

- 0.01445 X = - 0.141

X = 9.76 grams of Mg

what percentage of the alloy, by mass, is Mg??
( 9.76 grams of Mg) / (32.4 g sample ) = 30.1 % Mg