john want to buy a $ 100 trouser at the store , but he think it â € ™ s too expensive . finally , it goes on sale for $ 80 . what is the percent decrease ?
"the is always the difference between our starting and ending points . in this case , it â € ™ s 100 â € “ 80 = 20 . the â € œ original â €  is our starting point ; in this case , it â € ™ s 100 . ( 20 / 100 ) * 100 = ( 0.2 ) * 100 = 20 % . a"
subtract(100, 80)