In the equation the ratio of moles of CH4 to CHCl3 is equal, therefore there are equal moles present. Use the relative atomic mass of CHCl3 to work out how many moles are present and apply that to how many moles of CH4 are present. This can be done using the moles=mass/Mr. With the amount of moles of CH4 known, you can use the same equation to work out mass.