Accepted Answer
True, but only if the temperature of the gas doesn't change ... which is pretty hard to manage when you're compressing it.I think Boyle's law actually says something like (pressure) x (volume) / (temperature) = constant.So you can see that if you want to say anything about two of the quantities, you always have to stipulate that the statement is true as long as the third one doesn't change.
Suggested Answer
It's true, but the temperature of gas can NOT change.