Chemistry calcuation

from the information given we know that sulphur's mass is 21.47% of total mass, & looking at the periodic table we can see that sulphur has a mass of 32

to calculate the 21.47%, we'd have had to do 32/relative molecular mass x 100. if we call the relative molecular mass Mr for short, then we can solve for Mr

32/Mr x 100 = 21.47
32/Mr = 0.2147
32 = 0.2147Mr
Mr = 149

i hope this made sense i'm honestly crap at explaining things😭