Step 1: Identify who the question is about.
The question asks for the tax paid by Mrs. X.
Neither of the two statements mentions Mrs. X anywhere.
Step 2: Check statement I.
Statement I talks about Gauri and Rajat only, and compares Gauri's tax to Rajat's tax from last year.
It gives no link between Gauri or Rajat and Mrs. X. So it tells us nothing about Mrs. X's tax.
Step 3: Check statement II.
Statement II gives the amount Rajat paid this year, Rs. 9800.
Again, this is a fact about Rajat, not about Mrs. X. It gives no information connecting Rajat to Mrs. X.
Step 4: Check both statements together.
Even combining statement I and statement II, we only learn facts about Gauri and Rajat's tax payments across two years.
There is no data point, formula, or relation anywhere that connects Gauri or Rajat's tax to Mrs. X's tax.
So even together, the two statements do not let us find Mrs. X's tax.
Final Answer:
The question cannot be answered even using both statements together.
\[ \boxed{\text{Option (4)}} \]