Which effect is observed when the pressure of a gas increases?

$A$ home owner uses $4.00 \times 10^{3} \ m^{3}$ of methane $(CH_{4})$ gas (assume $CH_{4}$ is an ideal gas) in a year to heat his home. Under the pressure of $1.0 \ atm$ and $300 \ K$,the mass of gas used is $X \times 10^{5} \ g$. The value of $X$ is $.......$ (Nearest integer).
(Given $R = 0.083 \ L \ atm \ K^{-1} \ mol^{-1}$)

Calculate the volume of gas at $1.25 \ atm$,if the volume occupied by the gas at $1 \ atm$ and at the same temperature is $25 \ mL$. (in $mL$)

An open vessel at $27\,^oC$ is heated such that $\frac{3}{5}$ of the air in it is expelled. Assuming the volume of the vessel remains constant,calculate the temperature in $K$ to which the vessel was heated.

In the equation $PV = nRT$,which of the following is $NOT$ equal to the value of $R$?

At a temperature of $27\,^oC$ and a pressure of $1\,atm$,the density of a gas is $d$. At constant pressure,at what temperature will its density become $0.75\,d$?