A bag contains 7 white, 5 black and 4 red balls. Four balls are drawn without replacement find the probability that t least three balls are black.

Explanation

To find the probability that at least 3 balls drawn from the bag are black, we can break this down into two scenarios:

1. Exactly 3 balls are black.
2. Exactly 4 balls are black.

### Step 1: Calculate Total Number of Balls
First, we need to determine the total number of balls in the bag.

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