7 people average age is 30 . youngest person age is 8 . find average of the people when youngest was born .
"average age of people = 30 so have total age = 210 before 7 years we have to deduct each person age by seven years 210 - 56 = 154 so average age would be 154 / 7 = 22 answer : d"
divide(subtract(multiply(30, 7), multiply(8, 7)), 7)