Answer:

Step-by-step explanation:
Let x = number of books that Hannah donated
We know that the number of students is 150 and the total number of books is represented by b, we can write that as:
Average number of books donated by each student = 
Now we know that Hannah donated 3 times as much as the average. We can write that as:

12.74 is the answer to the question
36 feet + 9 feet
= 45 feet
You are correct! The distance from where Debbie and Andy are standing to the coral reef is 45 feet in total.