When a partner retires or dies, the gaining ratio is calculated as the difference between the new ratio and the old ratio of the remaining partners.
Step 1: Old ratio (equal sharing):
The firm originally shared profits and losses equally among Aditya, Vishesh, and Nimesh. The old ratio of Vishesh and Nimesh was:
\[
\text{Old ratio of Vishesh and Nimesh} = \frac{1}{3} : \frac{1}{3}.
\]
Step 2: New ratio (after Aditya's exit):
After Aditya's death, the new profit-sharing ratio of Vishesh and Nimesh was agreed to be \(4:3\).
Step 3: Gaining ratio:
The gaining ratio is calculated by subtracting the old ratio from the new ratio:
\[
\text{Vishesh's gain} = \frac{4}{7} - \frac{1}{3} = \frac{12 - 7}{21} = \frac{5}{21}.
\]
\[
\text{Nimesh's gain} = \frac{3}{7} - \frac{1}{3} = \frac{9 - 7}{21} = \frac{2}{21}.
\]
Thus, the gaining ratio is:
\[
\text{Gaining ratio of Vishesh : Nimesh} = 5:2.
\]
Conclusion:
The gaining ratio of Vishesh and Nimesh is \(5:2\).