Tony’s investments lost $12,545.50 in value over the past 2.5 months. On average, how much did his investments change each month? –$31,363.75

–$5,018.20

$5,018.20

$31,363.75

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! )