A compound of Fe and Cl is soluble in water. An excess of AgNO3 was added tp precipitate the Cl- as AgCl. if a 1.540g sample of the compund gave 4.082g AgCl, What is the formula of the compound?

Convert 4.082 g AgCl to g Cl.

That is 4.082 x (atomic mass Cl/molar mass AgCl) = about 1.00 g but you need to do that a bit ore accurately.
Then 1.540-1.00 = about 0.54.
Now convert those grams to mols and find the ratio of the elements to each other. The easy way to do that is to divide the smaller number by itself. Follow through by dividing the othr number by the same small number.
1.00/35.44 = ?
0.54/55.85 = ?
Find the ratio from the mols. Post your work if you get stuck.