The age of the father 4 years ago was 8 times the age of his son. At present, the father's age is 4 times that of his son. Find the present age of son.
In the following question, some part of the sentence may have errors. Find out which part of the sentence has an error and select the appropriate option. If a sentence is free from error, select 'No error'. The reason for (1)/ his failure is because (2)/ he didn't study at all. (3)/ No Error (4)