Larry read a 400
400400-page book. He read at a rate of
10
1010 pages per day for
d
dd days.
Write an equation that could be used to find out how many days it took Larry to read the book.

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! )