Question: Please show me the solution for: Mark is 18 years old. He has a little brother, John, who is 10 years younger. If John and Mark's parents are currently 5 times older than John, how old were they when Mark was born?
Answer: 
John is 8 years old because 18-10=8 years old.
Their parents are currently 40 years old because 8*5=40.
Therefore, they were 22 when Mark was born because 40-18 = 22 years old.