Explanation:

To solve this problem, we need to find Ritika's income (Rs.y) such that the combined tax rate of Suhani and Ritika is 37%. Let's go through the calculations:

- Suhani's income: Rs.90,000

- Suhani's tax rate: 30%

- Ritika's tax rate: 40%

- Total income combined tax rate: 37%

First, calculate Suhani's tax:

$$ \text{Tax paid by Suhani} = 30\% \times 90,000 = Rs.27,000 $$

Next, denote Ritika's income as y.

Her tax paid is:

$$ \text{Tax paid by Ritika} = 40\% \times y = 0.4y $$

Together, they have a combined income of:

$$ 90,000 + y $$

The total tax paid by both is:

$$ 27,000 + 0.4y $$

The combined tax rate can be calculated as:

$$ \frac{27,000 + 0.4y}{90,000 + y} = 37\% = 0.37 $$

Cross-multiply to solve for y:

$$ 27,000 + 0.4y = 0.37 \times (90,000 + y) $$

$$ 27,000 + 0.4y = 33,300 + 0.37y $$

Subtract 0.37y from both sides:

$$ 27,000 + 0.03y = 33,300 $$

Solve for y:

$$ 0.03y = 33,300 - 27,000 $$

$$ 0.03y = 6,300 $$

$$ y = \frac{6,300}{0.03} $$

$$ y = 2,10,000 $$

- Option 4: Rs.2,10,000 is indeed the correct value of y.

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