Help! Strange Question about empirical formulas and naming
An oxide of iron is found to be 77.75% iron by mass. Determine the empirical formula for this compound and name it.
Enter the formula with correct capitalization and subscripts (so "H2O" for H2O). Use all lowercase letters when typing names, no space before parentheses if parentheses are needed (so "tin(II) chloride")
I have tried to solve for the molar mass, but both oxygen and iron equal 1.39. Help?