You are correct! You correctly converted the 75.2 g of silicon dioxide to moles and then converted the moles of SiO₂ to 3.76 moles of C by the conversion factor 3 mol C/ 1 mol SiO₂. Then you converted the moles of carbon to grams of carbon by multiplying 3.76 mol C x 12.01 g C/1 mol C.