chemist makes 80.0g sulf trioxide by combining 50.0g oxygenwithunknown amountofsulfur.How chemistmake 100.0g sulf trioxide with no leftovers?

It is given that:
Mass ratio S : O₂ : SO₃ = (80.0 - 50.0) : 50.0 : 80.0 = 3 : 5 : 8

To make 100.0 g of SO₃ with no leftovers:
Mass of S needed = (100.0 g) × (3/8) = 37.5 g
Mass of O₂ needed = (100.0 g) × (5/8) = 62.5 g

100.0  X  32/80  =  40 g S  and 60 g O ...  you can provide the sig. figs.