Answer:
 B :step 2   she didnt collect all the like terms and calculate 
Step-by-step explanation:
first rewrite  remove all (  )Parentheses 
2nd   collect all like terms and calculate 
a^4 + 7a -16 -12^a^3 + 5a -3 
a^4 + 12a - 19 - 12a^3     ( Like terms are 7a +5a  and -16 +-3) 
so she skipped the second step
 
        
             
        
        
        
The tens place will be where the zero is which the value would be 70 since the 7 is in the thousand place the value is 7,000
        
             
        
        
        
We know, cos A + cos B = 2cos(C+D)/2 × cos(C - D)/2
So, 
cos 130 + cos 110 + cos 10
cos 130 + 2cos (110+10)/2 × cos( 110-10)/2 
cos 130 + 2cos 60 × cos 50
cos ( 180 - 50 ) + 2cos60 cos 50
We know, cos ( 180 - A ) = -cos A
2cos 60 cos 50 - cos 50
Also, cos 60 = 0.5
2×0.5 cos 50 - cos50
cos 50 - cos 50
0  = RHS.
Hence proved 
 
        
             
        
        
        
<span>most of the time it saids that s= a number.</span>
        
                    
             
        
        
        
Answer:
C)
Step-by-step explanation:
Find the total sum
25+28= 53
53+31=84
Fimd the average by dividing by 3
84/3= 28
Hence, the answer is c