Though incomplete in statement, the question requires the student to find x, that is, the number of molecules of water of crystallization.
Answer:
10
Explanation:
The masses of both anhydrous and hydrated salt was provided in the question as 0.474g and 1.279g respectively. These values are now substituted into the equation shown in the solution in the image attached. Solving that equation for x, the number of molecules of water of crystallization in Na2CO3.xH2O gives the answer as 10 as shown in the image attached.