There are 43.2 g of carbon to 14.4 g of hydrogen in a sample of methane (ch4). what percent of 37.8 g of methane is carbon?

Using the law of constant proportions  which says that within the same compound, elements exist in fixed ratios. 

Therefore; we can use the ratio of total mass to the mass of carbon, to determine the amount of carbon in another sample.

Mass C / Mass CH4 = Mass C / Mass CH4

43.2 g / 57.6 g = Mass C / 37.8 g

Mass C = 37.8 g × 43.2 g / 57.6 g 

              = 28.35 g

Hence; the percentage of carbon will be; 

=(28.35/ 37.8 )× 100%

= 75 % 

Thus; 75% of 37.8 g of methane is carbon