The Ideal Gas Equation is given by $PV = nRT$.

1. Analyze the Graph Axes: The problem specifies 'T-V curves', which implies Temperature ($T$) is plotted on the y-axis and Volume ($V$) on the x-axis.
2. Determine the Slope: Rearranging the ideal gas equation to express $T$ in terms of $V$: $T = \left(\frac{P}{nR}\right)V$. This equation represents a straight line passing through the origin ($y = mx$) where the slope $m = \frac{P}{nR}$.
3. Relate Slope to Pressure: The slope is directly proportional to the pressure ($m \propto P$). Therefore, the curve with the steepest slope corresponds to the highest pressure, and the curve with the lowest slope corresponds to the lowest pressure.
4. Conclusion: Assuming the lines are labeled 1, 2, and 3 in decreasing order of slope (as is standard for this specific PYQ where the answer is $P_1 > P_2 > P_3$), line 1 has the highest pressure and line 3 has the lowest. Thus, $P_1 > P_2 > P_3$.