12 years ago his age was x−12
12 years later his age will be x+12
As per problem the following equation can be formed
x+12=4(x−12)
⇒x+12=4x−48
⇒x−4x=−12−48
⇒−3x=−60
⇒x=20
His present age is 20 years.

A fan produces a feeling of comfort because our perspiration or sweating evaporates rapidly. Our body try to cool ourselves releasing sweat through pores of skin. And when we sit under the fan the sweat evaporates due to directed air upon us making our body cool as evaporation is the cooling process.