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.
A student cycles 2 km North, then turns West and cycles 2.5 km, then turns South and cycles 2 km, then turns to his left and cycles 4.5 km. Where is he now with respect to the starting position?
In a certain code language, '÷' represents '+', '-' represents 'x', '+' represents '÷' and 'x' represents '-'. Find out the answer to the following question.