Suppose the volume of a balloon decreases so that the temperature of the balloon decreases from 280K to 240 K and its pressure drops from 1.6 × 10^4 Pa to 1.7 × 10^4 Pa. What is the new volume of the gas?
PV/T is constant, so you want V such that
1.7*10^4 V/240 = 1.6*10^4 * Vo/280
So what was the original volume Vo ?