eighteen years ago , a father was 3 times as old as his son . now the father is only twice as old as his son . then the sum of the present ages of the son and the father is :
let the present ages of the father and son be 2 x and x years respectively . then , ( 2 x - 18 ) = 3 ( x - 18 ) x = 36 . required sum = ( 2 x + x ) = 3 x = 108 years . answer is c
add(subtract(multiply(multiply(multiply(const_2, const_3), const_3), 3), multiply(multiply(const_2, const_3), const_3)), multiply(subtract(multiply(multiply(multiply(const_2, const_3), const_3), 3), multiply(multiply(const_2, const_3), const_3)), const_2))