PLEASEEE HELP WITH MATH, ITS SIMPLE AND EASYY

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! )

Write as a product of two polynomials. 2(3–b)+5(b–3)^2

(30 points). the population of a city is 45,000 and decreases 2% each year. if the trend continues, what will the population be aer 15 yrs