A box contains 12 copybooks. Some of the copybooks are priced at 500 L.L. each, and the others are priced at 750 L.L. each. The total price of all the copybooks is 8000 L.L. The problem asks us to find the number of copybooks of each price type.

1. Problem Description

A box contains 12 copybooks. Some of the copybooks are priced at 500 L.L. each, and the others are priced at 750 L.L. each. The total price of all the copybooks is 8000 L.L. The problem asks us to find the number of copybooks of each price type.

2. Solution Steps

Let $x$ be the number of copybooks priced at 500 L.L. each, and let $y$ be the number of copybooks priced at 750 L.L. each.

We are given two pieces of information:

\begin{enumerate}

\item The total number of copybooks is

1

2. \item The total price of all copybooks is 8000 L.L.

\end{enumerate}

From the first piece of information, we can write the following equation:

$x + y = 12$

From the second piece of information, we can write the following equation:

$500x + 750y = 8000$

We have a system of two linear equations with two variables:

\begin{cases}

x + y = 12 \\

500x + 750y = 8000

\end{cases}

We can solve this system of equations using substitution or elimination. Let's use substitution. From the first equation, we can express $x$ in terms of $y$:

$x = 12 - y$

Now, substitute this expression for $x$ into the second equation:

$500(12 - y) + 750y = 8000$

$6000 - 500y + 750y = 8000$

$250y = 8000 - 6000$

$250y = 2000$

$y = \frac{2000}{250}$

$y = 8$

Now, substitute the value of $y$ back into the equation $x = 12 - y$:

$x = 12 - 8$

$x = 4$

So, there are 4 copybooks priced at 500 L.L. each and 8 copybooks priced at 750 L.L. each.

3. Final Answer

There are 4 copybooks priced at 500 L.L. each and 8 copybooks priced at 750 L.L. each.