A sample of gas has a volume of 2.00 L and a pressure of 0.750 kPa when its temperature is 25°C. If the volume is expanded to 4.00 L and the pressure reduced to
0.500 kPa, what must the temperature become?
379°C
397°C
379 K
397K

hope this helps :) and sorry its so long

Explanation:

In order to design hot air balloons like these, engineers must make gas law calculations, buoyancy calculations, and have knowledge of the density of air at different altitudes.

These three gas laws can be combined into the Combined Gas Law as follows:

A commonly used form of the combined gas law states that, for a sample of gas, the ratio of the product of the original pressure and volume to the original temperature will equal the ratio of the product of a new pressure and volume to the new temperature, or

This equation is useful when operating with the same sample of gas, and given five of the variables, to solve for the sixth.