A father is now three times as old as his son. Three years back, he was four times as old as his son. The age of the son (in years) is  Pick
A) A)12  B) B)9  C) C)18  D) D)20  E) E)22
Explanation:   Let son's age be x years. Then, father's age = (3x) years.   Three years ago, father's age = (3x - 3) years and son's age = (x - 3) years.   So, 3x - 3 = 4 (x - 3)=&gt; 3x - 3 = 4x - 12=&gt; x = 9.   Answer: 9
<result>B</result>
A father is now three times as old as his son. Three years back, he was four times as old as his son. The age of the son (in years) is