Question

The mass of a carbon atom is 2 x 10^-21 g.
How many carbon atoms are there in 6g of carbon?​

Answer 1

You must divide mass of carbon by mass of carbon atom.

$\dfrac{6\mathrm{g}}{2\cdot10^{-21}\mathrm{g}}=3\cdot10^{21}=3\mathrm{Z}$

There are 3 zetta atoms of carbon in 6g of carbon.

Hope this helps.