Answer:
1.23*10^-6 g Au
Step-by-step explanation:
take your atoms and divide by Avogadro's number to get number of moles
3.75 x 10^15 / 6.022 x 10^23 = 6.227 x 10^-9 moles
multiple the moles by molar mass of Au to get grams Au
6.227 x 10^-9 moles * 196.966 = 1.226*10^-6
round to 3 sig fig