Answer:

 

         1.      15 + 2(10) = 35

                  3(10) = 30

                  The second method is cheaper.

 

         2.      15 videos

                  15 + 2(15) = 45 and 3(15) =45


         Some students may draw a table to show their answer. Example:

 

$15 membership fee and $2 to rent a video

Number of videos

0

1

5

10

15

20

Cost for videos

$15

$17

$25

$35

$45

$55

 

No membership fee and $3 to rent a video

Number of videos

0

1

5

10

15

20

Cost for videos

$0

$3

$15

$30

$45

$60