Matching inverse operations​

Abacteria population is tripling every hour. by what factor does the population change in 1/2 hour? select all that apply

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! )

Acompany that makes? hair-care products had 5000 people try a new shampoo. of the 5000 ? people, 35 had a mild allergic reaction. what percent of the people had a mild allergic? reaction?