As the hint says the first thing we have to do is to determine the molar mass of our compound. To do so we need the molar mass of one atom of each element present in our compound.
molar mass of Ec = 31.79 g/mol
molar mass of H = 1.01 g/mol
molar mass of O = 16.00 g/mol
Since one molecule of Ec₂H₄0₆ has 2 atoms of Ec, 4 atoms of H and 6 atoms of O, we can find the molar mass of Ec₂H₄0₆ like this:
molar mass of Ec₂H₄0₆ = 2 * molar mass of Ec + 4 * molar mass of H + 6 * molar mass of O
molar mass of Ec₂H₄0₆ = 2 * 31.79 g/mol + 4 * 1.01 g/mol + 6 * 16.00 g/mol
molar mass of Ec₂H₄0₆ = 163.62 g/mol
Now we can find the number of moles that we have in 127.49 g of Ec₂H₄0₆.
number of moles = mass of sample/molar mass
number of moles = 127.49 g / (163.62 g/mol)
number of moles = 0.7792 moles
Answer: Therea are 0.7792 moles in 127.49 g of our compound.