Question

A single atom of platinum has a mass of 3.25 x 10^-22 g. What is the mass of 6.0 x 10^23 platinum atoms?

Answer 1

You're given mass of one atom, simply multiple by 6.0x10^23 for total mass
Side note: 6.0 x 10^23 is commonly known as Avagadro's Number, aka. a "mole"

Answer 2

\[\text{Pt}[\text{atom}]=3.25\times10^{-22}[\text{g}]\]
\[6\times10^{23}\times\text{Pt}[\text{atom}]=6\times10^{23}\times3.25\times10^{-22}[\text{g}]=(6\times3.25)\times10^{(23-22)}[\text g]\]