[Asaph]

A salt whose formula is Na₂SxOy,is 47.5% by mass .
Find x.

I tried to set it at 100g eith 47.5g sulfur and thus
Putting the rest at combined 52.2g ,
Then im stucked, two unknowns here,

A little help

[Borek]

Try trial and error (assume some small values of x, y and calculate S mass percentage for each).

Your approach is not bad, but won't get you past the fact it is impossible to easily translate fact that x and y are integers into an equation.