Question

Staples sells boxes of pens ($18) and rubber bands ($6). Leona ordered a total of 20 cartons for $300. How many boxes of each did Leona order?

Answer 1

-Let be "p" the number of boxes of pens that Leona ordered and "r" the number of rubber bands she ordered.

According to the information given in the exercise:

- The cost of 1 box of pens is $18 and the cost of 1 box of rubber bands is $6.

- Leona ordered 20 cartons.

- The total cost was $300.

Answer 2

-Let be "p" the number of boxes of pens that Leona ordered and "r" the number of rubber bands she ordered.

According to the information given in the exercise:

- The cost of 1 box of pens is $18 and the cost of 1 box of rubber bands is $6.

- Leona ordered 20 cartons.

- The total cost was $300.

Using this information you can set up the following System of Equations:

`\begin{cases}18p+6r=300 \\ p+r=20\end{cases}`

In order to solve it, you can apply the Elimination Method:

1. Multiply the second equation by -6.

2. Add the equations.

3. Solve for "p".

Then:

`\begin{gathered} \begin{cases}18p+6r=300 \\ -6p-6r=-120\end{cases} \\ ------------- \\ 12p+0=180 \\ \\ p=(180)/(12) \\ \\ p=15 \end{gathered}`

4. Substitute the value of "p" into the second original equation.

5. Solve for "r".

Then:

`\begin{gathered} p+r=20 \\ (15)+r=20 \\ r=20-15 \\ r=5 \end{gathered}`

Therefore, the answer is: Leona ordered 15 boxes of pens and 5 boxes of rubber bands.