The sum of two numbers:
x + y = 108
The difference of the same two numbers:
x - y = 78
We can use substitution to figure out x and y:
x - y = 78 can be changed to x = 78 + y
We can plug this into the first equation:
78 + y + y = 108
78 + 2y = 108
2y = 30
y = 15
Now solve for x using any of the two equations. I'll use the first equation since it's easier:
x + 15 = 108
x = 93
 
        
             
        
        
        
Answer is in the pic above. Theorems used:
Exterior angle theorem
Inscribed angle theorem. 

 
        
             
        
        
        
Answer:
Is there any more to this question?
Step-by-step explanation: 
 
        
                    
             
        
        
        
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Answer:
Two squares with the same side lengths are always congruent.
Two quadrilaterals with the same side lengths are always congruent.
Two rectangles with the same side lengths are always congruent.
Step-by-step explanation: