1 mol of Carbon = 12 grams.
x mol of Carbon = 55 grams
12*x = 1 * 55
x = 55/12
x = 4.583333 mols of carbon
1 mol of anything is 6.02 * 10^23 atoms
4.58333333 mol = x
1/4.5833333 = 6.02 * 10^23/x
x = 4.58333* 6.02*10^23
x = 2.7591 * 10^23 Carbon atoms