Concept:The series follows a constant difference pattern where each term decreases by the same number.Explanation:Subtract 5 from the first term to get the second: 20 - 5 = 15.Subtract 5 from the second term to find the missing term: 15 - 5 = 10.Check further: 10 - 5 = 5, and 5 - 5 = 0, which matches the given series.Thus, the missing number is 10.
