I’d need to know the question to answer this.
Answer:

Step-by-step explanation:
Everything is distributed evenly on both ends.
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(n-1)-3 = (3n)/2 This is the equation used to represent the information given
Step-by-step explanation:
so he already down 20 ft so he ascends (goes up) 9 feet, so hes at 11 feet right now. then he descends 12 (goes down) feet so hes at 23 feet. lastly he ascends 15 feet (goes up) more. so the answer is 8