Yes, sorry I meant that there is a solid, not a solid metal.

Here is my work:

I calculated the number of grams of hydrogen based off of the number of mols of acetic acid. Since dividing 75 grams by the molar mass of acetic acid (60 g/mol) gives you the number of mols (1.25 g/mol) and we know that for every mol of acetic acid there are 2 mols of h2 so we multiply 1.25 by 2. So we have 2.5 mols of h2, and the molar mass of h2 is 2 g/mol. We multiply both these numbers and we get 5 grams of of h2. Now, we can plug everything back into the equation, and we get that the metal should be 43.4 grams. After converting this to amu (I used an online calculator) you get 26.1 amu, which is closest to aluminum.