Answer: 
Step-by-step explanation:
The formula for finding the nth term of an arithmetic sequence is given as:

first term = -15
common difference = -6 - (-15) = 9
number of terms
substituting into the formula , we have :


Answer:
The expression to determine the total cost in dollars is
.
Step-by-step explanation:
Given:
Service charge to make a photo book = $20
Cost per extra page = $0.75
Cost to ship the complete photo book = $5
We need to write expression to determine the total cost in dollars.
Solution:
Let the number of extra pages be denoted by 'x'.
Also Let the Total cost be denoted by 'y'.
Now we can say that;
Total cost will be equal to sum of Service charge to make a photo book and Cost per extra page multiplied by number of extra pages and Cost to ship the complete photo book.
framing in equation form we get;

Hence the expression to determine the total cost in dollars is
.
To do this i add them uo and easily subtract woth a hand held calculator