Answer:
A. (it's on step 2 of my explanation.
Step-by-step explanation:
I attached a picture for the explanation since i'm assuming you need help understanding how it's solved.
1. since 6.022*10 ^22 atoms of mg is 1 MOLE
2. have to find the moles of mg. so you divide 7.43*10^22 by 6.022*10^22
(you will get .123 moles of mg.
3. to get the mass of Mg, you need to multiply the moles of mg(.123) and the molar mass (amu) of mg (24.30)
Ps. idk y i wrote it out and typed it out. I just felt like i wasn't clear enough on my attached image so... let me know if this helped. (: