Answer:

Step-by-step explanation:
A sequence that has a common difference is an <em>arithmetic sequence</em>:

where aₙ is the nth term, n is the index, and d is the common difference.
In your question:
Plug those into the formula:

Then solve:

Correct, because $.6 per ounce works for all of the number of ounces. Times 0.6 for all of the number of ounces on the left side (5,10,15,20) to find the result (cost of detergent)
y=.6x
The answer to #5 is 1540
The answer to #6 is 17017