Answer
$1.7\times10^{22}\ atoms\ Au$
Work Step by Step
1. The percentage represents the number of ounces of gold per 100 grams of bracelet. Use this as a conversion factor in order to find the number of ounces of gold. Then convert ounces into grams. Next, use the molar mass of gold in order to find the number of moles of gold atoms in the bracelet. Finally, use Avogadro's number to find the total number of gold atoms.
$$0.255\ oz-bracelet\times\frac{75oz-Au}{100oz-bracelet}\times\frac{435g\ Au}{16oz\ Au}\times\frac{1\ mol Au}{196.966\ g\ Au}\times\frac{6.022\times10^{23}\ atoms Au}{1\ mol Au}$$
$$=\ 1.7\times10^{22}\ atoms\ Au$$
