Boyle's law is a gas law which states that the pressure and volume of gas has an inverse relationship, when the temperature remains constant. This means that when the pressure of the gas increases the volume decrease and vice versa. The equation for this is P1 x V1=P2 x V2. P1 is the initial pressure of the gas and P2 is the new pressure of the gas. V2 is the initial volume of the gas and V2 is the new volume of the gas. Another way to write the formula is PV=K. In this case P= the pressure of the gas, V=the volume of the gas, and k=a constant. This formula means that for a given mass the product of the pressure and volume is consistent. So when the pressure triples the volume is divided by three.
This picture is a representation of Boyle's law. Its saying as pressure increases volume will decrease and as volume increases the pressure will decrease.