A number is doubled and 9 is added. If resultant is trebled, it becomes 51. What is that number
Answers:
A) 4
B) 10
C) 12
D) 14
E) 15

Rationale: "explanation : = > 3 ( 2 x + 9 ) = 51 = > 2 x + 9 = 17 = > x = 4 answer : option a"
Answer: A