On strong heating, 12g of NaHSO4 release 0.9g of water vapour and a white solid is left. Deduce a chemical formula for the solid.

How can I work this out?

Thanks :)

12.0 g initially

11.1 g after heating
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0.9 g H2O released.
0.9/molar mass H2O = mols H2O
11.1/molar mass NaHSO4 = mols NaHSO4.
Find the mols ratio to obtain the formula. Post your work if you need help through the calculations.