The law was formulated by John Dalton in $$1801$$. It states that the total pressure exerted by the mixture of non-reactive gases is equal to the sum of the partial pressures of individual gases, i.e, the pressure which these gases would exert if they were enclosed separately in the same volume and under the same condition of temperature. In a mixture of gases, the pressure exerted by the individual gas is called partial pressure.
Mathematically,
$$P_{Total}=P_{1}+P_{2}+P_{3}$$ (at constant $$T,V$$)
Where, $$P_{Total}$$ is the total pressure exerted by the mixture of gases and $$P_{1},P_{2},P_{3}$$etc, are partial pressure of gases.
Or,
According to Dalton's law of partial pressure, "Total exerted pressure by mixture of all non-reactive gases is equal to the sum of partial pressure of all individual gases".
At constant temperature $$T$$ and volume $$V$$,
$$P_{Total}=P_{1}+P_{2}+P_{3}$$
Where, $$P_{Total}=$$ total exerted pressure of mixture of all gases.
$$P_{1},P_{2},P_{3}$$ is pressure exerted by individual gases known as partial pressure.