I think it’s C but I’m not entirely sure..hope I helped
        
             
        
        
        
Y = mx + b
m = (y2 - y1)/(x2 - x1)
y = (26,600 - 18100)/(20 - 10)x + b
y = 850x + b
18100 = 850(10) + b
b = 9600
R(x) = 850x + 9600
        
             
        
        
        
1. 2x + 50 = 100
subtract 50 on both sides and then divide by 2. 
x = 25
180 - 100 = 80
m
2. 7x - 4 = 87
add 4 on both sides and divide by 7.
x = 13
180 - 87 = 93
m
3. 5x - 2 = 38
add both sides by 2 and divide by 5.
x = 8
180 - 38 = 142
m
4. 14 + 6x = 134
subtract both sides by 14 and divide by 6.
x = 20
180 - 134 = 46
m
5. x = 53
 m
6. x = 14
 m