Answer: Choice D) 
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Work Shown:

Explanation:
First I subtracted y/b from both sides. Then I multiplied both sides by 'a' to fully isolate x. You can optionally distribute the 'a' through to each term inside the parenthesis, but your teacher has chosen not to do this.
 
        
             
        
        
        
Answer:
x = -2, y = 3
Step-by-step explanation:
Given equations are,
4x + 5y = 7 ---------(1)
3x - 2y = -12 ----------(2)
Multiply equation (1) by 3
12x + 15y = 21 ------(3)
Multiply equation (2) by (-4)
-12x + 8y = 48 --------(4)
Now add equations (3) and (4),
(12x + 15y) + (-12x + 8y) = 21 + 48
(12x - 12x) + (15y + 8y) = 69
23y = 69
y = 3
From equation (2),
3x - 2(3) = -12
3x - 6 = -12
3x = 6 - 12
x = -2
Therefore, x = -2 and y = 3 will be the answer.
 
        
                    
             
        
        
        
Answer:
why no links? also I think the answer is 5 but I'm just guessing
 
        
                    
             
        
        
        
Here x=3
so, putting 3 instead of x
 
 
        
        
        
SAS i believe :) sorry if im wrong!