Answer:
I was going to give the answer but i keep getting it wrong, I am so sorry for wasting your time. IK i shouldn't be answering if I dont have the answer but i need the points. I feel terrible about this. 
Step-by-step explanation:
 
        
             
        
        
        
The answer is b 
Because you have to add da x and dat is 2x den add da numbers which is 4
        
             
        
        
        
First you need to get x on one side of the equation and to do that subtract 2a from both sides.
28 + 2a = 5a + 7
 -2a -2a
28=3a+7
Then we need to get a alone by subtracting 7 on both sides.
28=3a+7
-7 -7
21=3a
Finally divide each side by 3 and you should get a = 7. Hope this helps!
        
             
        
        
        
Ok -7-7=-14 because your subtracting a negative with a negative and then it will be a negative then if you multiply a negative and a negative it will be a positive