The sum of two numbers is 51. The larger number is 19 more than the smaller number

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! )

In september, louise planted a tree. every month, the tree louise planted grew 2 inches. what would the constant of proportionality of the line be?

Arectangle has a perimeter of 24 inches. if the width is 5 more than twice the length, what are the dimensions of the rectangle?