One of the ways to find the answer is to find how much 1 percent of 150 is. To do that we just have to divide 150 by 100:
150 / 100 = 1.5
Now we can divide 9 by 1.5 to know how much percent of 150 it is:
9 / 1.5 = 6
Let's check it:
150 * 6% = 150 * 6/100 = 15 * 6/10 = 3 * 6/2 = 18/2 = 9
It's correct then :)