A number is doubled and 9 is added. If the resultant is trebled, it becomes 147. What is that number?

Question: A number is doubled and 9 is added. If the resultant is trebled, it becomes 147. What is that number?

Solution:
Let the number be x

According to the question,
3(2x + 9) = 147
⇒ 6x + 27 = 147
⇒ 6x = 147 - 27
⇒ 6x = 120
⇒ x = 120/6
∴ x = 20

Hence, the number is 20.