This is an ideal gas problem. The gas inside the balloon is considered ideal. Ideal gas equation is a function pressure, temperature, amount and volume. Note: amount is constant since the balloon ins closed. Pressure is maintained constant since the walls are flexible. Ideal gas equation is: PV=nRT. Put all constant in one side and variables in one.
P/nR=T/V. To find the answer to the question equate the constants of both situation T1/V1=T2/V2 (25+273.15)/3=(x+273.15)/2 x=-74.38 degC
Electrons are the only thing that can freely move from one object to another object. By rubbing the silk cloth on the glass, since the net charge becomes positive, that means that electrons were removed. So answer is : electrons removed.