The answer is -33.6 degree Celsius... or approximately-34 degree Celsius. Firstly, you will change the L to mL so 2.10L to mL is 2100ML.. so if 750ML=-12 degree Celsius then 2100ML is what?? So.. if more less divide.. so 2100ML/750ML *-12 =-33.6 degree Celsius.. approximately -34 degree Celsius. I hope it helped??