Answer:
C. -1
Step-by-step explanation:
f(x) = 2/ (-x-1) 
As we can see, f(x) is a fraction with two components: numerator (2) and denominator (-x-1). 
According to the theorem, the fraction only exists when its denominator is different from 0. 
So that in this situation, (-x-1) has to be different from 0
- x - 1 ≠0 
=> - x≠ 1
=> x ≠ -1 
So that if x = -1, (-x-1) = 0, making the fraction not exist. 
So the input is not allowed is x = -1
 
        
             
        
        
        
89.25 is the original price first i did 75÷100=0.75×51=38.25+51=89.25 is the correct answer.