Geometry

Question Analysis
This question involves calculating the probability of mutually exclusive events within the context of a numbered - marble drawing.
The main focus is on recognizing that a marble's number cannot be both less than 7 and greater than 15 at the same time, making these two events mutually exclusive.

Key Concept Explanation
The concept of mutually exclusive events is crucial here.
When two events have no common outcomes, they are mutually exclusive.
For such events, the probability of either event occurring is the sum of their individual probabilities. .

Step - by - Step Solution
Determine the number of favorable outcomes for each event.
For the event of drawing a marble with a number less than 7 (event ), the favorable numbers are 1, 2, 3, 4, 5, 6. So, there are 6 favorable outcomes, and .
For the event of drawing a marble with a number greater than 15 (event ), the favorable numbers are 16, 17, 18, 19, 20. So, there are 5 favorable outcomes, and

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