Let's begin by listing out the information given to us:
There are four students: n = 4
Number of students to be selected: r = 2
To calculate the combination of 2 students to be chosen, we use:

Therefore, there 12 possible combinations from these
17 goes into 34 two times
and goes into 0 zero times
So 340 / 17 = 20
Answer
19?
Step-by-step explanation:
Answer:
38%
Step-by-step explanation:
Original price = $ 80
Price after reduction = $ 49.60
Reduction = 80 - 49.60 = $30.40
Percentage of decrease = 

= 38%