Explanation:

- The problem provides the combined cost of 4 digital cameras and 6 mobile phones as Rs. 51,365.

- You are asked to find the cost of 12 digital cameras and 18 mobile phones.

- Notice that 12 digital cameras and 18 mobile phones are exactly three times the initial quantities.

- Thus, to find this cost, simply multiply Rs. 51,365 by 3.

- Doing the math:

- 51,365 x 3 = 1,54,095

- Hence, the correct option is Option 3: Rs. 1,54,095 .