Boyles Law is certainly proved. This question highlights the importance of knowing the application of Boyles Law. Boyles law states that "For a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume are inversely proportional." Here, having a fixed amount of gas is very important to note, as under this strict condition only Boyles Law is applicable. When you blow a balloon, you are increasing the amount of gas (or the number of moles are increasing), due to which Boyles Law is not obeyed in this condition.