if the mean age of Jeruto and her parents is 26,
the total age of 3 of them must be 26x3 = 78
27 + 30 = 57 ( current total ages of her parents )
78 - 57 = 21 ( remaining number of years all of them need to age )
since there are 3 of them, they age 3 years in 1 year.
21 / 3 = 7
answer = 7 more years.
