Please help me Fairly simple Geometry question!

Lisa has three classes that each last 50 minutes. what is the total number of minutes of the three classes

I’m confused on how to work the pie charts

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! )