An electronis store had 20% off sale. if a sterreo originally cost 125, how much

20% percent refers to the rate
So to find 20% off of $125 you have to multiply the rate by the original price and then subtract that number from the original price
First you have to make the percent into a decimal. To do that you have to move the decimal point over to the left two times or divide by 100:
20/100= .20
So the equation would be:
.20 • 125= 25
Now you have to subtract from the original number:
125-25=100
So the answer would be that the stereo would cost 100 with the 20% off sale