Ten years ago, the average age of A and B was 20 years. The average age of A, B and C is 30 years today. How old will C be after 5 years?

Step 1: Find the sum of the current ages of A and B.

Ten years ago, sum of ages of A and B = 2 × 20 = 40

Current sum of ages of A and B = 40 + 10 + 10 = 60

Step 2: Find the current age of C.

Current sum of ages of A, B, and C = 3 × 30 = 90

Current age of C = 90 - 60 = 30

Step 3: Find the age of C after 5 years.

Age of C after 5 years = 30 + 5 = 35

Answer: (C) 35