Ty bought a pair of jeans at a 25% off sale. he paid $22.50 before tax for the jeans. what was the original price of the jeans

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! )