Volume of Liquids

Q.

At a particular temperature, a certain quantity of a gas occupies a volume of $74{\mathrm{cm}}^3$ at a pressure of$760\mathrm{mm}$. If the pressure is decreased to$740\mathrm{mm}$, what will be the volume of the gas at the same temperature?

Q.

While stating the volume of a gas, the pressure and temperature should also be given. Why?