1ST you do 12 divided by 100 = 0.12 then you multiply 15. 0.12 x 15 = 1.80 then you do $12-$1.80= $10.80. You get 15% is $1.80 off the original price. So $12 with the discount would be $1.80. S= $12-0.15*1.80
$16 with the discount would be $ 2.40.
$20 with the discount would be $ 3.00
$25 with the discount would be $ 3.75
I hope that helps.
I am sorry if it is wrong.