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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 [tex]\( h \)[/tex], the weight of the hardcover book, and [tex]\( p \)[/tex], the weight of the paperback?

[tex]\[
\begin{array}{l}
h = 4.2 - p \\
h = 2p
\end{array}
\][/tex]

A.
[tex]\[
\begin{array}{l}
h = p - 4.2 \\
h = 2p
\end{array}
\][/tex]

B.
[tex]\[
\begin{array}{l}
h = 4.2 - p \\
p = 2h
\end{array}
\][/tex]

C.
[tex]\[
\begin{array}{l}
h = p - 4.2 \\
p = 2h
\end{array}
\][/tex]

D.
[tex]\[
\begin{array}{l}
h = 4.2 - p \\
h = 2p
\end{array}
\][/tex]


Sagot :

Let's examine the given problem and determine the correct system of equations.

### Problem Statement
1. The hardcover version of a book weighs twice as much as its paperback version.
2. The hardcover book and the paperback together weigh 4.2 pounds.

Let's denote:
- [tex]\( h \)[/tex] as the weight of the hardcover book.
- [tex]\( p \)[/tex] as the weight of the paperback book.

From the problem statement, we can infer the following equations:
1. The hardcover book weighs twice as much as the paperback version. This can be written as:
[tex]\[ h = 2p \][/tex]
2. The total weight of the hardcover book and the paperback book is 4.2 pounds. This can be written as:
[tex]\[ h + p = 4.2 \][/tex]

Now, we need to examine the given options and see which system of equations matches our inferences.

### Options Analysis

1. [tex]\(\begin{array}{l} h=p-4.2 \\ h=2p \end{array}\)[/tex]

The first equation [tex]\(h = p - 4.2\)[/tex] does not align with our inference that [tex]\( h + p = 4.2 \)[/tex]. Therefore, this is not the correct system.

2. [tex]\(\begin{array}{l} h=4.2-p \\ p=2h \end{array}\)[/tex]

The second equation [tex]\(p = 2h\)[/tex] does not align with our inference that [tex]\(h = 2p\)[/tex]. Therefore, this is not the correct system.

3. [tex]\(\begin{array}{l} h=p-4.2 \\ p=2h \end{array}\)[/tex]

Neither of these equations aligns with our inferences. Therefore, this is not the correct system.

4. [tex]\(\begin{array}{l} h=4.2-p \\ h=2p \end{array}\)[/tex]

Both equations align perfectly with our inferences:
- [tex]\(h = 4.2 - p\)[/tex] represents the total weight equation rearranged.
- [tex]\(h = 2p\)[/tex] represents the relationship between the weights of the hardcover and paperback versions.

Therefore, the correct system of equations to use is:
[tex]\[ \begin{array}{l} h=4.2-p \\ h=2 p \end{array} \][/tex]

This correctly models our problem statement and will allow us to solve for [tex]\(h\)[/tex] and [tex]\(p\)[/tex].