Three years ago, the average of A, B, and C was 27 years and that of A and C, 5 years ago was 20 years. B’s present age is-

Question: Three years ago, the average of A, B, and C was 27 years and that of A and C, 5 years ago was 20 years. B’s present age is-

Solution:
Three years ago, the average of A, B, and C was 27 years old
total age 3 years ago = (27 × 3) = 81 years
So, at present their total age is = 81 + 3 + 3 + 3 = 90 years

average of A and C, 5 years ago was 20 years
total age 5 years ago = (20 × 2) = 40 years
At present, total age of A and C is = 40 + 5 + 5 = 50 years

∴ B's present age is = 90 - 50 years = 40 years