This answer is not correct. I think that just used the 3 moles of carbon from the balanced equation and multiplied this by the mass of carbon. You first need to convert the 75.2 g of silicon dioxide to moles and then convert the moles of SiO₂ to moles of C by the conversion factor 3 mol C/ 1 mol SiO₂. Then convert the moles of C obtained to grams.