Answer:
Because there is only one out put for each domain this mapping diagram is a function. 
Step-by-step explanation:
Two sets are involved.  There is a directional property, the relation is defined from one set called the domain on to another set called the codomain. A function is a relation that has exactly one output for each input in the domain.
 
        
             
        
        
        
Step-by-step explanation:

According to this trigonometric function, −C gives you the OPPOSITE terms of what they really are, so be EXTREMELY CAREFUL:
![\displaystyle Phase\:[Horisontal]\:Shift → \frac{-\frac{2}{3}π}{2} = -\frac{π}{3} \\ Period → \frac{2}{2}π = π](https://tex.z-dn.net/?f=%5Cdisplaystyle%20Phase%5C%3A%5BHorisontal%5D%5C%3AShift%20%E2%86%92%20%5Cfrac%7B-%5Cfrac%7B2%7D%7B3%7D%CF%80%7D%7B2%7D%20%3D%20-%5Cfrac%7B%CF%80%7D%7B3%7D%20%5C%5C%20Period%20%E2%86%92%20%5Cfrac%7B2%7D%7B2%7D%CF%80%20%3D%20%CF%80)
Therefore we have our answer.
 Extended Information on the trigonometric function
![\displaystyle Vertical\:Shift → D \\ Phase\:[Horisontal]\:Shift → \frac{C}{B} \\ Period → \frac{2}{B}π \\ Amplitude → |A|](https://tex.z-dn.net/?f=%5Cdisplaystyle%20Vertical%5C%3AShift%20%E2%86%92%20D%20%5C%5C%20Phase%5C%3A%5BHorisontal%5D%5C%3AShift%20%E2%86%92%20%5Cfrac%7BC%7D%7BB%7D%20%5C%5C%20Period%20%E2%86%92%20%5Cfrac%7B2%7D%7BB%7D%CF%80%20%5C%5C%20Amplitude%20%E2%86%92%20%7CA%7C)
NOTE: Sometimes, your vertical shift might tell you to shift your graph below or above the <em>midline</em><em> </em>where the amplitude is.
I am joyous to assist you anytime.
 
        
                    
             
        
        
        
Answer:
-x+20=31
Step 1: Subtract 20 from both sides.
−x+20−20=31−20
−x=11
Step 2: Divide both sides by -1.
−x
−1
=
11
−1
x=−11
Answer:
x=−11
 
        
                    
             
        
        
        
X=-4             you have to substitue first so you put the equation where the X is and then you would distribute and then add the numbers that have the common exponent