Correct option is D
Let x be the number. According to the problem, when x is increased by 9, it becomes equal to three times half of the number.
x + 9 = 3(x/2)
Solving for x, we get:
X + 9 = 3X/2
Or, 2x + 18 = 3x
Or, x = 18
Therefore, the number is 18.