The hardcover version of a book weighs twice as much as its paperback version. the hardcover book and the paperback together weigh 4.2 pounds. which system of equations can be used to find h, the weight of the hardcover book, and p, the weight of the paperback? h = p − 4.2 h = 2p h = 4.2 − p p = 2h h = p − 4.2 p = 2h h = 4.2 − p h = 2p

We can let p be the amount of the paperback and h be the amount of one hardcover version. Now, we can express the statements in terms of p and h. Since the hardcover costs twice as much as the paperback version, we have h = 2p.
 
And since it's also given that the total weight of a paperback and hardcover is 4.2, we have p + h = 4.2.

Summarizing the system of two equations, we have

 Rearranging this, we have


Hence, we have the system of equations needed to solve for the values of p and h.

 h = 4.2 - p || h = 2p

First subtract 10 from both side
y^2+6y-16=0
(y+8)(y-2)=0
-8 and 2