Amuseum gives tours to students in groups of seven for six grade classes are going to the museum today there are 20 students in class with three students are absent today and museum is to determine the number of groups select trust falls street

I'm at a bookstore with $\$35$ in my pocket and a $20\%$-off coupon. what is the cost of the most expensive book i can buy with my money and the coupon? (assume that there are books of every possible price in the bookstore. it's a large bookstore! )