How do i solve a problem dealing with percentages?
example: 10% of $50.00
it's become very frustrating because google says this is the formula: sale price = original price × (1 - percent off%)
i really don't understand how the formula works.

Okay 

Lets say you got a discount of 20% on a 40 dollar bike

To get the answer of how much off the bike is multiple 40 and 20%

In math if you are about to multiply a percent to a whole number put a decimal in front of it.

Example :

.20 × 40 = 8

So the bike is 8 dollars off

If you want to find the new price after the discount just subtract the answer ( 8 )

40 ( the original price ) - 8 ( the discount total )

The answer would be 32

The new price for the bike adding the discount would be $32.oo