Answer: The answer is either 4, 12, 36 or 100, 60, 36.
Step-by-step explanation: Let the first two numbers be 'a' and 'b'.
According to the question, a, b and 36 forms a geometric series. So, we have
Also, if 36 is replaced by 20, then a, b, 20 will form an arithmetic series. So,
Therefore,
Thus, the three numbers are either 4, 12, 36 or 100, 60, 36.