159,99 -20%
( 1 - 20% ) * 159,99
= ( 1 - 0,2 ) * 159,99
= 0,8 * 159,99
= 127,992
159,99 - 20% * 159,99
= 159,99 - 0.2 * 159,99
= 159,99 - 31,998