When you use negative numbers (Numbers that start with a negative sign (-)), the bigger the number after the negative, the smaller the number and also a negative number is always less than a positive number. This means that Joe's score beats Dena's score, because Joe's score is negative and Dena's score is positive, so Joe's score is lesser than Dena's score.
You multiply the 4.00 by 0.10 to get the 10% discount amount. Then you subtract that from $4.00. Then you multiply that amount by 1.06 to get the total with the 6% sales tax. To get $3.82 rounded to the nearest cent.