Hello from MrBillDoesMath!
Answer: 40%
Discussion:
Let's ask an easier question. What is 1/2 or 50% of the number 150?. It's 75. Since 75 is larger than the problem's 60 we need to look for a slightly smaller percentage than 50%. The choice of 40% seems evident.
Another approach:
60 = (x/100) 150
so x = (60/150) * 100 = 40 %
Regards, MrB