Basic Inorganic Chemistry Question Help

[pyroglycerine]

This question is translated from Chinese so forgive he possible bad wording. Also the question may not make sense, if this is so, please tell me.

 

At 0C mercury in a barometer reaches 760mm. Upon changing the pressure, 3ml of air enters the tube of the barometer causing the mercury level to drop to 570mm. Calculate the volume of air that occupies the barometer.

 

I have no idea where to begin wih this question, it was hard enough translating it. If you think it doesnt make sense and have a suggestion of what they might be trying to ask then please go ahead. Any help at all will be great.

 

Thanks

在0C时气压计内汞柱高760mm, 在该压力时，通空气3ml入管内汞柱降至570mm,求这时空气在气压计内所占体积.

If by any luck you are Chinese, that is the original question.

[chemadict]

uhm,so when at 0 degree celsius, the mecury is 76 cm tall, changing the air presure will cause the liquid to drop....