Answer:
A and B are functions
Step-by-step explanation:
for A, none of the x's repeat which makes it a FUNCTION
for B, when it starts with x^2, it will always be a FUNCTION (its a quadratic)
for C, 10 repeats for the x so it is NOT A FUNCTION
 
        
             
        
        
        
You’re answer is 21 
7(3)= 21 I hope I’m right :))