You have a frame that holds three pictures. You pulled out your favorite five photos. How many sets of three are there? Make a list of all the possible combinations using the numbers 1 to 5 to represent the photos.

C(5,3)=10

Pictures 1,2,3,4,5

So the Possible sets are:

(1,2,3) (1,2,4)

(1,2,5) (1,3,4)

(1,3,5) (1,4,5)

(2,3,4) (2,3,5)

(2,4,5) (3,4,5)

n=9

step-by-step explanation:

7 times a number = 7n

decreased by 13 = 7n-13

same as is =

5 times the number = 5n

increased by 5 = 5n+5

7n-13 = 5n+5

2n=18

n=9