Asample of carbon-12 has a mass of 6.00 g. how many atoms of carbon-12 are in the sample?

i have the answer but i don't understand how to solve it.

Carbon - 12 :  m = 6.00 g
From the Periodic system:  Molar mass of C - 12 : M = 12 g / mol
n = m / M = 6 g / 12 g/mol = 0.5 mol ( the number of moles )  
N a = 6.02 * 10 ^23  mol^(-1) ( Avogadro`s constant )
N = n * N a = 0.5 mol  * 6.02 * 10 ^23 = 3.01 * 10^23

3.01 * 10^23 atoms of Carbon -12 are in the sample.

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