A bag contains 7 white, 5 black and 4 red balls. If two balls are drawn at random, find the probability that: (i) both the balls are white (ii) one ball is black and the other red (iii) both the balls are of the same colour.

Explanation

To solve the problem step by step, we will calculate the required probabilities for each part of the question.

### Given:
- Number of white balls (W) = 7
- Number of black balls (B) = 5
- Number of red balls (R) = 4

### Total number of balls:
...