**According to Boyle's Law,**

At constant temperature( $T)$ and number of moles of $\operatorname{gas}(\mathrm{n})$, the volume $(V)$ bears an inverse relation with the pressure(P) exerted by a gas.
$$
V \propto \frac{1}{P}\ldots \ldots \ldots \ldots \ldots \ldots \ldots(1)
$$

**According to Charles's Law,**

When pressure(P) exerted by the gas and number of moles of gas $(n)$ are constant, then volume $(V)$ of gas bears a direct relation with Temperature.

$$\mathbf{V} \propto \mathrm{T}\ldots \ldots \ldots \ldots \ldots \ldots \ldots(2)$$

**According to Avogadro's Law,**

When temeprature $(T)$ and pressure $(P)$ exerted by the gas are constant, then volume of gas bears a direct relation with number of moles of gas(n).

$$\mathbf{V} \propto \mathbf{n}\ldots \ldots \ldots \ldots \ldots \ldots \ldots(3)$$

**Combining equation (1) (2) & (3)**

$$V \propto n T / p$$

**Ideal Gas Equation → P V= nRT....(R is Universal gas constant =8.314)**