a number is doubled and 9 is added . if the resultant is trebled , it becomes 51 . what is that number ?
"let the number be x . then , 3 ( 2 x + 9 ) = 51 2 x = 8 = > x = 4 answer : e"
divide(subtract(51, multiply(const_3, 9)), multiply(const_3, const_2))