Write ideal gas equation.

Explanation

### Step-by-Step Solution:

1. **Understanding the Ideal Gas Equation**: The ideal gas equation relates the pressure (P), volume (V), and temperature (T) of an ideal gas. It can be expressed in the form of a ratio that compares two different states of the gas.

2. **Writing the Equation**: The ideal gas equation can be represented as:
\[ \frac{P_1 V_1}{T_1} = \frac{P_2 V_2}{T_2} \]
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