How To Calculate Percentage Without Calculator?

I do a long and stupid way that's kind of like proportions, because I learned how to do it on my own self taught weird ways..
There are better ways out there but in case you don't find them, I do it like this:

X /100 = y / h

you want to fill in the blank of x and use the y and h as the number's you're comparing it to. Hopefully this makes sense. Then you solve it in some loop pattern. This is going to sound pretty wild, but here's an example:

X / 100 = 2 / 6

and you want to figure out what 2/6th percentage is, you will start with the 100, multiply it by 2, and then divide it by 6...(which is why I call it the loop thing, because I actually draw the path out on the paper so I don't get confused) when you finally reach X, it's 33.3

For example if  i work at a retail store and do not have a calculator an item cost  $79.99  and is 30 % off how do i figure it out  with out a calculator.

If the given value is   -   38/45
multiply the numerator & denominator with 100
you'll get    -   3800/4500
the divide with 45 the denominator and numerator
you ll get the answer 84.4/100 ie 84.4%

I don't understand how to solve this problem