Let x1,x2,x3,x4 and x5 be the present ages of the family comprising of 5 members 3 years ago, (x1+x2+x3+x4+x5)−3×5=80 ⇒ (x1+x2+x3+x4+x5)−15=80....(i) Now, let the age of new born baby be x6 Given, Average age of family today = Average age of family 3 years ago ⇒