A person has a 30 percent chance of winning on a scratch-off lottery ticket. What is the probability she first wins of the fifth ticket? ( 5/1 ) (0.30)3 (0.70)
( 5/4 ) (0.70)3 (0.30)
(0.70)^4 (0.30)
(0.30)^3 (0.70)
0.30

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! )