Math how can calculation

can any one tell me please how can find out like full price was $40.00 and sale price 12.00 how much is discount?

The previous answer is correct- the amount of the discout is 28%. If you want it as a percentage, you put the amount saved over the original price and express it as a percentage:
28/40 *100% = 7/10*100%= 70%

These answers u guys gave are idiotic,

Here's how

First if 40$ x percent off (P) = 12

Then look at it like this

40 x P = 12
P= 12/40
P= 3/10

3/10= 30 percent off

If u want to check ur work, plug in 40 times .3 in the calc you should get 12

well how much was taken off? 40-12= 28
Ok so 40 * A = 28

a simple equation where you have one unknown.
A=28/40= 7/10 =.70 = 70%

for a percentage it would be 100-(12÷40)x100) the answer would be 70% discount :)

Afsfs, that means your only paying 30%, eg 70% off...