Final answer:
In Boyle's Law, the pressure of a gas is inversely proportional to its volume. The law states that as the volume of gas increases, the pressure decreases, and as the volume decreases, the pressure increases. This relationship holds true as long as the temperature and quantity of gas remain constant.
Step-by-step explanation:
(a) The term 'inversely proportional' means that as one variable increases, the other variable decreases, and vice versa. In the case of Boyle's law, as the volume of a gas increases, the pressure decreases, and as the volume decreases, the pressure increases.
(b) The 'other things' that must be equal are the temperature and the quantity of gas. Boyle's law states that the pressure of a gas is inversely proportional to its volume, but to maintain the validity of the law, the temperature and the quantity of gas must remain constant.