Answer:
???
Step-by-step explanation:
 
        
                    
             
        
        
        
Answer: 100
Step-by-step explanation:
 
        
                    
             
        
        
        
Answer:
Here's the simplest example possible: let's say x + y = 3 and x - y = 1. Solve the second equation for x by adding y to both sides: (x - y) + y = 1 + y. So x = 1 + y. Take that value of x, and substitute it into the first equation given above (x + y = 3).