Find P (A or B) if the events are disjointed. P (A) = 6/25, and P (B) = 9/25.

Here, "disjointed" signifiies that Event A and Event B are independent; neither outcome influences the other. In such a case, the union of A and B is given by the sum of the two probabilities P (A) and P (B).

Here, that sum is P (A or B) = 6/25 + 9/25, or 15/25, or 0.6.

He was correct he just forgot to simplify it which it would be 3/5