Explanation:

Sure! Let's break down the problem:

- Kamal and her sister together have Rs 2,100. This means their combined amounts total Rs 2,100.

- Let Kamal's initial amount be K and her sister's initial amount be S. So, K + S = 2100.

- If Kamal takes Rs 300 from her sister, Kamal’s new amount becomes K + 300 and her sister’s new amount becomes S - 300.

- According to the problem, K + 300 = S (Kamal will have the same amount as what her sister had earlier).

Let's solve these equations:

- From K + 300 = S, we get S = K + 300.

- Substitute S = K + 300 in K + S = 2100:

- K + (K + 300) = 2100

- 2K + 300 = 2100

- 2K = 1800

- K = 900

So, initially, Kamal had Rs 900 and her sister had Rs 1200.

- Ratio of Kamal's amount to her sister's amount initially is 900:1200 = 3:4.

- Option:1, 3:4 is the correct answer.