Find the age of Seventh Person

Let x= Total age of 6 people. x/6=43
x=258

y= age of 7th man.
(x+y)/7 =45; substitue x in this eqn. then y=57

19 yrs.

Present avg age of 6 persons is 45,
After 2 yrs the avg age of 6 persons will be 47.
To make it 43 subtract 4 from each.
Hence 4*6=24 is left , this is to be added to7th person's age to make the avg 43
so, 24 + 7th persn's age = 43,
Therefore, 7th person's age= 43-24=19.

avg age of 6 persons after 2 yrs  will be 43,
hence present avge age of 6 persons should be 41,   (= 246/6)

when 7th person has joined  avg is 45,   (=315/7)

hence 7th person's age will be   (315- 246)= 69yrs.