Question

75 grams of SO2? 4 FeS + 7 O2 → 2 Fe2O3 + 4 SO2

Answer 1

You need to learn how to ask a question. Do you want to know how much FeS is needed to produce 75 grams SO2? or how many grams of O2 are needed to produce 75 grams SO2. Or something different. I will assume you want to know how many grams SO2 are needed to produce 75 grams SO2.

mols SO2 in 75 grams SO2 = g/molar mass = 75/32 = approx 2.3 but you need to do that more accurately. Now convert mols SO2 to mols O2 needed. 2.3 mols SO2 x (7 mols O2/4 mols SO2) = 2.3 x 7/4 = ?
Post your work if you get stuck.