The relationship between moles and volume, when pressure and temperature of a gas are held constant, is: v/n =
k. we could say then, that:
if the moles of gas are tripled, the volume must also triple.
if the moles of gas are halved, the volume must be doubled.
if the moles of gas are doubled, the volume must be halved.
if the moles of gas are doubled, the volume is unaffected.

If the moles of gas are tripled, the volume must also triple.

Explanation:

According to Avogadro law,

Equal volume of all the gases at same temperature and pressure have equal number of molecules.

The number of moles and volume are directly related to each other. By increasing the number of moles volume also goes to increase with same ratio.

When number of moles decreases the volume also goes to decrease at constant temperature and pressure.

Mathematical expression:

V ∝ n

V = Kn

V/n = k

When volume is changed from V₁ to V₂ by changing the number of moles from n₁ to n₂. Then expression will be,

V₁/n₁ = V₂/n₂

i do not get it   at all