Let's solve the problem step by step. The question can be translated as follows:

Question:
Lina buys three notebooks and one pen for Rp17,000. Ani buys two notebooks and one pen for Rp12,000. How much should Nana pay if she buys one notebook and one pen?

Define the variables:

• Let $x$ represent the price of one notebook.
• Let $y$ represent the price of one pen.

Step 1: Write the equations based on the information.

1. From Lina's purchase: $3x + y = 17,000$
2. From Ani's purchase: $2x + y = 12,000$

Step 2: Subtract the equations to eliminate $y$:

$(3x + y) - (2x + y) = 17,000 - 12,000$ $x = 5,000$

Step 3: Substitute $x = 5,000$ into one of the original equations to find $y$.

Using $2x + y = 12,000$: $2(5,000) + y = 12,000$ $10,000 + y = 12,000$ $y = 2,000$

Step 4: Calculate the cost for Nana.

Nana buys one notebook and one pen, so the total cost is: $x + y = 5,000 + 2,000 = 7,000$

Final Answer:

Nana must pay Rp7,000.

Would you like me to explain any step in more detail or solve a similar problem? Here are 5 related questions for further practice:

1. What if Nana buys two notebooks and two pens?
2. How many pens can Lina buy with Rp17,000 if she doesn't buy any notebooks?
3. If the price of a pen increases by Rp1,000, what will be the new price Nana has to pay?
4. How much would Ani pay if she bought four notebooks and two pens?
5. Solve for $x$ and $y$ if Lina spent Rp20,000 instead of Rp17,000 for the same items.

Tip: When solving a system of equations, check the coefficients to decide whether substitution or elimination is easier!