I need to find the relationship between Andrew's age and his grandfather's age. Let me call Andrew's age x and his grandfather's age y. Then I can write two equations based on the information given: y = 12x and y = 55 + x. I can substitute y = 12x into the second equation and get 12x = 55 + x. Subtracting x from both sides, I get 11x = 55. Dividing both sides by 11, I get x = 5. That means Andrew is 5 years old now. 
Andrew's grandfather's age is twelve times Andrew's age. If Andrew's grandfather was 55 years old when Andrew was born, how many years old is Andrew now?