Question 15

Explanation

Creating a Mathematical Model

Let:

• $x$ = price of meat per kg
• $y$ = price of fish per kg

Based on the table, we can create a system of two linear equations.

For Store A:

For Store B:

Finding the Price of Fish

We will find the value of $y$ (price of fish). Eliminate variable $x$ from equations $(1)$ and $(2)$.

Multiply equation $(1)$ by $7$ and equation $(2)$ by $4$ so that the coefficients of $x$ are the same:

Subtract the two equations:

Therefore:

Since the unit in the table is "thousand rupiah", the price of fish is $20$ thousand rupiah or $\text{Rp}20,000.00$.

Thus, the price of fish per kilogram is $\text{Rp}20,000.00$.