The task is to generate the correct answer for a given math problem.
--------
Question: Problem: a bullet train covers a distance in 50 min , if it runs at a speed of 48 kmph on an average . the speed at which the bullet train must run to reduce the time of journey to 40 min will be .

Answer: 60 kmph

Question: Problem: meena wrote all the numbers from 1 to 29,999 inclusive . how many digits did she write in total ?

Answer: 138,889

Question: Problem: a father is now 3 times as old as his son . 8 years back , he was 4 times as old as his son . the age of the son ( in years ) is

Answer:
24