Here's another way to look at it.
Percent means 'out of one hundred' so.....
think of it like this...
one out of eight is how many out of 100?
1/8 = ?/100
From here you can multiply both sides by 100. On the right side, the 100 on the top will cancel the 100 on the bottom of the fraction because 100/100 = 1 and 1 times anything doesn't change that thing's value. So ?/100 times 100 = just ?
On the left side of the equation, we get
100 times 1/8. 100 times 1 is 100 so we're left with 100 / 8. We get the answer 12.5 percent.
A double check:
1 divided by 8 = .125
When we substitute the 12.5 for the ? above,
12.5 divided by 100 = .125 also!