It's a word problem.

When air expands without gaining or losing heat, it's pressure P and volume V are related by the equation PV^1.4=C (c is constant). Instant volume is 400 cm^3 and pressure is 80kPa and is decreasing at a rate of 10kPa/min. At what rate is the volume increasing at this instant?

Should I solve for V and the take the derivative? What is the answer worked out?

Thankies, first time doing these types of problems.