Copper is one of a group of metals called the coinage metals. How many atoms of copper (Cu) are in a pure copper coin weighing 12.0 g?

Answer 1

I don't think there are any modern coins that are pure copper. Even the penny, formerly pure Cu consists mostly of Zn now. So forgetting coins, if you want to know the atoms in 12.0 g pure Cu (of anything), that is as follows:
mols Cu = g/atomic mass = 12.0/63.54 = 0.189
1 mol contains 6.02E23 atoms so 0.189 will contain 6.02E23 x 0.189 = ?

Answer 2

the answer is 1.14x10^23