Five positive whole number, which are not necessarily all different, are written on 5 different cards. Peter calculates the sum of each pair of cards. He obtains only 3 different results, 57, 70, and 80. What is the biggest number written on the cards? A) 35 B) 42 C) 48 D) 53 E)8

First convert 75% to a number by moving the decimal place to the left two places. That gives us .75. Now to figure out what 75% of $8 is we multiply .75 by 8. You should end up with $6. Now you subtract the discounted price from the original and it gives you $8-$6=$2.