I am failing math!!
Algebra 1

How do i put 3(x+7) in distributive property

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! )

Ineed to know the ordered pairs for this equation i need the answer quick because it’s a timed test