Question 366896
6x - 3 = 8x - 9  |subs 6x on both side 
 
6x - 3 - 6x = 8x - 9 - 6x
 
-3 = 2x - 9 | +9 on both side
 
6 = 2x, two times x is six, hence x = 3
 
 
Verification : 
 
 6*3 - 3 = 18 - 3 = 15 (LHS)
 
 8*3 - 9 = 24 - 9 = 15 (RHS)