Verified Answer :

In the said law, the
volume of a gas varies inversely with pressure. Boyle's law is one of the gas
laws we have. According to this law, at a fixed amount of an ideal gas which is
at constant temperature, the pressure and volume are inversely proportional
with each other. The variables are volume and pressure.

Answer: Pressure and volumes are the variables in Boyle's law.

Explanation:

Boyle's law states " The pressure of gas is inversely proportional to the volume occupied by the gas when the temperature(in kelvins) is held constant ".

\(P\propto \frac{1}{V}\)

\(PV=\text{constant}\)

Which means that, with increase in the volume of gas the pressure exerted by the gas decreases or vice versa.

Here variables were pressure and volume.