Experts pls resolve this problem

dear student,
Molar mass of salt = (2 X 23) + 32 + (16 X 4) + x X 18
= 142 + 18 x
On heating it will lose water and become anhydrous. 55.9 % mass is the mass of water in Na₂SO₄.xH₂O.
Mass by mass % = (mass / molar mass of compound) X 100
mass of water = 18 x

55.9 = (18 x / 142 + 18 x) X 100
55.9 (142 + 18 x) = 1800 x
7937.8 + 1006.2 x = 1800 x
x = 9.99
x = 10 (approx.)
So, the molecular formula of compound is Na₂SO₄.10H₂O
Thus, the correct option is (d).
regards