Given that ∠ABD = 71°, which equation could be used to solve problems involving the relationships between ∠DBC and ∠ABC?
A)	(4a + 12) = (6a + 9)	
B)	71 = (4a + 12) + (6a + 9)	
C)	(4a + 12) − (6a + 9) = 71	
D)	(4a + 12) + 71 = (6a + 9)
                                             
                                          
                                          
                                        
											 
					                  