1. 
                                    elimination\:x+y=3,\:x-y=1
                                
                                
                                    1. 
                                    elimination\:x+y=3,\:x-y=1
                                
                                                            
                                    2. 
                                    elimination\:x+y=7,\:x-y=5
                                
                                
                                    2. 
                                    elimination\:x+y=7,\:x-y=5
                                
                                                            
                                    3. 
                                    elimination\:y=-2,\:-3y+4x=18
                                
                                
                                    3. 
                                    elimination\:y=-2,\:-3y+4x=18
                                
                                                            
                                    4. 
                                    elimination\:x+y=150,\:x=y+260
                                
                                
                                    4. 
                                    elimination\:x+y=150,\:x=y+260
                                
                                                            
                                    5. 
                                    elimination\:x-y=3,\:x+y=21
                                
                                
                                    5. 
                                    elimination\:x-y=3,\:x+y=21
                                
                                                            
                                    6. 
                                    elimination\:12x+2y=7,\:y=x+5
                                
                                
                                    6. 
                                    elimination\:12x+2y=7,\:y=x+5
                                
                                                            
                                    7. 
                                    elimination\:x+y=8,\:x-y=-4
                                
                                
                                    7. 
                                    elimination\:x+y=8,\:x-y=-4
                                
                                                            
                                    8. 
                                    elimination\:8x-2y=12,\:7x+3y=15
                                
                                
                                    8. 
                                    elimination\:8x-2y=12,\:7x+3y=15
                                
                                                            
                                    9. 
                                    elimination\:60x-40y=30,\:-40x+90y=-10
                                
                                
                                    9. 
                                    elimination\:60x-40y=30,\:-40x+90y=-10
                                
                                                            
                                    10. 
                                    elimination\:12x+13y=9,\:15x-23y=6
                                
                                
                                    10. 
                                    elimination\:12x+13y=9,\:15x-23y=6