There are a few ways to figure out this answer. 12.5% is the same as 1/8.
So to get the answer you can either divide 16 by 8, or you can get there the other way, and divide 12.5 by 100 and then multiply that result by 16.
When figuring the answer out in your head, think about the number 12.5. It is half of 25%, which is half of 50%, which is half of 100%. So, you take the 16 and take away half, then half again, and then half again.