How many grams are in 6.59 x 10^24 atoms of carbon

First, you need to find how much moles does 6.59*10^24 atoms of Carbon represents.
The Avogadro number represents one mole of a substance. The Avogadro number is about Na=6.02*10^23.
So, to find the mole number, you divide the number of atoms you have by the Avogadro number: n=N/Na (n=number of mole, N=number of atoms, Na=Avogadro Number).
So n=6.59*10^24/6.02*10^23 = 10.94 moles.

So to find the mass in grams of a certain number of moles, you multiply the mole number by the Molar mass of the substance you're studying.
m=n*M (m=mass in grams, n=number of moles, M=Molar mass)
The molar mass of the carbon is 12.01 g/mol.
So m=10.94 * 12.01 = 131.38 grams.

So There's 131.38 grams in 6.59*10^24 atoms of Carbon.

Hope this Helps! :)