K would be 13 I hope his helps
        
             
        
        
        
P = 3n + 30
p = 75
75 = 3n + 30
45 = 3n
n = 15
A customers earns 15 additional points on purchasing one shirt.
        
                    
             
        
        
        
36...
<span>divide your 16 by 4, so that you have 1/9. You then multiply the resulting number(4) by your denominator, 9. 4 times 9 = 36</span>
        
                    
             
        
        
        
The value of x from the given equation is 5/3
<h3>How to determine the value</h3>
Since the three points are collinear to U, they are on a straight line which equals 0
Then we have,
UM + UD =  MD
5x+30 + 10x+20 = 3x+80
Collect like terms
5x + 10x + 50 = 3x + 80
15x - 3x = 80 - 50
12x = 30
x = 30/12 = 15/6 = 5/3 
Thus, the value of x from the given equation is 5/3
Learn more about collinear points here:
brainly.com/question/18559402
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There would be 14 female and 7 male, so the total number of students is 21.