Well depending on how you look at you could do $40 plus that extra 20% and since you said that means to add you would do the same price. as the actual price before you add that thirty 20% so you would add 40 plus 40 equals 80. If you did 25% the you would add 40 and 40 which is 80 and that's 20%out of 25% and add 5 to 80 and you get $85.