The average cost of streaming N movies will be
.. average cost = (total cost)/(number of movies)
.. = (50 +5N)/N
.. = (50/N) +5
You want this value to be 7, so you have
.. 7 = (50/N) +5
.. 2 = 50/N
.. N = 50/2 = 25
25 movies must be streamed to get the average cost down to $7.
To answer this question, an assumption must be made, that Eva spends 8 hours a day working. If this is the case, then Eva will complete jobs w, x, and v on day one, for a total of six hours. Since the next job (y) requires 4 hours, she will spend two hours working that day, leaving 2 more hours to go on that job. The next day she will spend 2 hours finishing job y, completing it, and finish the longest job z (hours) that day. This means she had 4 jobs on day one, and 2 jobs on day 2 for and average of 3 jobs per day.
This answer assumes an 8 hour work day, and that Eva can start a job she cannot finish that day.
The rule is -3, then +2
24-3 = 21
21 + 2 = 23
23-3= 20
20+2= 22
22-3= 19
19+2 = 21
21-3= 18
18+2 = 20
F(x) represents how many pages in total Antonia has read, while x represents the number of days.